De update naar Yosemite 10.10.3. heeft mij mijn dag gekost en de zaken verergerd! 
Probleem is naast de bekende Wifi-perikelen, nu:
1. Insufficient Permission Errors
2. Kan files niet meer downloaden, saven, trashen
3. Kan geen nieuwe folders meer aanmaken.
Heb Permissies proberen te herstellen met Disk Utility, Repair Disk Permissions, en zapping PRAM > geen resultaat.
Re-install via de combo-install > ook geen resultaat.
Dit is EtreCheck report.
Misschien kunnen jullie hier wijs uit.
EtreCheck version: 2.1.8 (121)
Report generated April 9, 2015 at 10:47:51 PM GMT+2
Download EtreCheck from http://etresoft.com/etrecheck
 
Click the [Click for support] links for help with non-Apple products.
Click the [Click for details] links for more information about that line.
 
Hardware Information: ℹ️
    MacBook Pro (Retina, 13-inch, Mid 2014) (Technical Specifications)
    MacBook Pro - model: MacBookPro11,1
    1 2.6 GHz Intel Core i5 CPU: 2-core
    8 GB RAM Not upgradeable
        BANK 0/DIMM0
            4 GB DDR3 1600 MHz ok
        BANK 1/DIMM0
            4 GB DDR3 1600 MHz ok
    Bluetooth: Good - Handoff/Airdrop2 supported
    Wireless:  en0: 802.11 a/b/g/n/ac
    Battery Health: Normal - Cycle count 283
 
Video Information: ℹ️
    Intel Iris
        Color LCD spdisplays_2560x1600Retina
 
System Software: ℹ️
    OS X 10.10.3 (14D131) - Time since boot: 0:37:18
 
Disk Information: ℹ️
    APPLE SSD SD0128F disk0 : (121.33 GB)
        EFI (disk0s1) <not mounted> : 210 MB
        Recovery HD (disk0s3) <not mounted>  [Recovery]: 650 MB
        Macintosh HD (disk1) / : 120.14 GB (23.57 GB free)
            Encrypted AES-XTS Unlocked
            Core Storage: disk0s2 120.47 GB Online
 
USB Information: ℹ️
    Apple Internal Memory Card Reader
    Apple Inc. Apple Internal Keyboard / Trackpad
    Apple Inc. BRCM20702 Hub
        Apple Inc. Bluetooth USB Host Controller
 
Thunderbolt Information: ℹ️
    Apple Inc. thunderbolt_bus
 
Gatekeeper: ℹ️
    Mac App Store and identified developers
 
Kernel Extensions: ℹ️
        /Library/Application Support/Avast/components/fileshield/unsigned
    [loaded]    com.avast.AvastFileShield (2.1.0 - SDK 10.10) [Click for support]
 
        /Library/Application Support/Avast/components/proxy/unsigned
    [loaded]    com.avast.PacketForwarder (2.0 - SDK 10.10) [Click for support]
 
        /System/Library/Extensions
    [not loaded]    com.devguru.driver.SamsungComposite (1.4.28 - SDK 10.6) [Click for support]
    [not loaded]    com.wacom.kext.wacomtablet (6.3.8 - SDK 10.9) [Click for support]
 
        /System/Library/Extensions/ssuddrv.kext/Contents/PlugIns
    [not loaded]    com.devguru.driver.SamsungACMControl (1.4.28 - SDK 10.6) [Click for support]
    [not loaded]    com.devguru.driver.SamsungACMData (1.4.28 - SDK 10.6) [Click for support]
    [not loaded]    com.devguru.driver.SamsungMTP (1.4.28 - SDK 10.5) [Click for support]
    [not loaded]    com.devguru.driver.SamsungSerial (1.4.28 - SDK 10.6) [Click for support]
 
Launch Agents: ℹ️
    [not loaded]    com.adobe.AAM.Updater-1.0.plist [Click for support]
    [running]    com.adobe.AdobeCreativeCloud.plist [Click for support]
    [running]    com.avast.update-agent.plist [Click for support]
    [loaded]    com.avast.userinit.plist [Click for support]
    [running]    com.wacom.wacomtablet.plist [Click for support]
 
Launch Daemons: ℹ️
    [running]    com.adobe.adobeupdatedaemon.plist [Click for support]
    [loaded]    com.adobe.fpsaud.plist [Click for support]
    [loaded]    com.avast.init.plist [Click for support]
    [loaded]    com.avast.uninstall.plist [Click for support]
    [loaded]    com.avast.update.plist [Click for support]
 
User Launch Agents: ℹ️
    [loaded]    com.adobe.AAM.Updater-1.0.plist [Click for support]
    [loaded]    com.adobe.ARM.[...].plist [Click for support]
    [loaded]    com.avast.home.userinit.plist [Click for support]
    [loaded]    com.google.keystone.agent.plist [Click for support]
 
User Login Items: ℹ️
    Garmin Express Service    Application  (/Applications/Garmin Express.app/Contents/Library/LoginItems/Garmin Express Service.app)
    iTunesHelper    Application Hidden (/Applications/iTunes.app/Contents/MacOS/iTunesHelper.app)
    Google+ Auto Backup    Application  (/Applications/Google+ Auto Backup.app)
    KiesAgent    Application Hidden (/Applications/Kies.app/Contents/MacOS/KiesAgent.app)
    fuspredownloader    Application Hidden (/Users/[redacted]/Library/Application Support/.FUS/fuspredownloader.app)
 
Internet Plug-ins: ℹ️
    AdobeAAMDetect: Version: AdobeAAMDetect 2.0.0.0 - SDK 10.7 [Click for support]
    FlashPlayer-10.6: Version: 16.0.0.305 - SDK 10.6 [Click for support]
    QuickTime Plugin: Version: 7.7.3
    AdobePDFViewerNPAPI: Version: 11.0.10 - SDK 10.6 [Click for support]
    AdobePDFViewer: Version: 11.0.10 - SDK 10.6 [Click for support]
    Flash Player: Version: 16.0.0.305 - SDK 10.6 Outdated! Update
    Default Browser: Version: 600 - SDK 10.10
    WacomTabletPlugin: Version: WacomTabletPlugin 2.1.0.6 - SDK 10.9 [Click for support]
 
User internet Plug-ins: ℹ️
    Picasa: Version: 1.0 - SDK 10.6 [Click for support]
    Google Earth Web Plug-in: Version: 7.1 [Click for support]
 
Safari Extensions: ℹ️
    Avast Online Security
    searchtab
 
3rd Party Preference Panes: ℹ️
    Flash Player  [Click for support]
    WacomTablet  [Click for support]
 
Time Machine: ℹ️
    Auto backup: YES
    Volumes being backed up:
        Macintosh HD: Disk size: 120.14 GB Disk used: 96.57 GB
    Destinations:
        LaCie [Local]
        Total size: 1.00 TB
        Total number of backups: 2
        Oldest backup: 2014-12-15 16:52:40 +0000
        Last backup: 2014-12-24 08:24:33 +0000
        Size of backup disk: Excellent
            Backup size 1.00 TB > (Disk size 120.14 GB X 3)
 
Top Processes by CPU: ℹ️
         9%    firefox
         4%    WindowServer
         1%    com.avast.fileshield
         1%    fontd
         0%    com.avast.daemon
 
Top Processes by Memory: ℹ️
    885 MB    firefox
    318 MB    Finder
    163 MB    com.avast.daemon
    146 MB    mds_stores
    146 MB    WindowServer
 
Virtual Memory Information: ℹ️
    707 MB    Free RAM
    3.88 GB    Active RAM
    3.00 GB    Inactive RAM
    1.01 GB    Wired RAM
    7.74 GB    Page-ins
    811 KB    Page-outs
 
Diagnostics Information: ℹ️
    Apr 9, 2015, 10:09:47 PM    Self test - passed
    Apr 9, 2015, 10:02:52 PM    /Library/Logs/DiagnosticReports/installd_2015-04-09-220252_[redacted].cpu_resou rce.diag [Click for details]
    Apr 9, 2015, 09:47:18 PM    /Users/[redacted]/Library/Logs/DiagnosticReports/fontd_2015-04-09-214718_[redac ted].crash
    Apr 9, 2015, 09:26:24 PM    /Library/Logs/DiagnosticReports/com.apple.AmbientDisplayAgent_2015-04-09-212624 _[redacted].crash
    Apr 9, 2015, 08:47:18 PM    /Library/Logs/DiagnosticReports/AdobeCrashDaemon_2015-04-09-204718_[redacted].c rash
    Apr 9, 2015, 12:22:09 PM    /Library/Logs/DiagnosticReports/AdobeCrashDaemon_2015-04-09-122209_[redacted].c rash
MacBook Pro with Retina display, OS X Yosemite (10.10.3)