virtualbox.org

I just installed 4.3.26 and am trying to install and update a brand new Windows 7 Guest OS.

With network settings set to NAT, the Win 7 Guest OS stays connected to the network, but my Mac OS X Yosemite host loses all network functionality.

Anyone else seen this? I didn't see anything in the forums related to this

Do you mean networking or access to the internet? I've been running VB on Yosemite since 6/14. Are you running OSX 10.10.3?

Yep, 10.10.3 (14D131)

So what networking functionality do you mean?

This thread seems to have died but I am having a networking problem in that there is no networking on any virtual machine, WinXP, Win7, Win10 and Ubuntu, I'm not sure when this started as I don't use VB that often but the Yosemite update to 10.10.4 seems likely point.

Following from OS X console log:
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02/05/2015 16:58:28.868 VirtualBox[54432]: WARNING: The Gestalt selector gestaltSystemVersion is returning 10.9.4 instead of 10.10.4. Use NSProcessInfo's operatingSystemVersion property to get correct system version number.
Call location:
02/05/2015 16:58:28.868 VirtualBox[54432]: 0 CarbonCore 0x00007fff875d02b7 ___Gestalt_SystemVersion_block_invoke + 113
02/05/2015 16:58:28.869 VirtualBox[54432]: 1 libdispatch.dylib 0x00007fff91646c13 _dispatch_client_callout + 8
02/05/2015 16:58:28.869 VirtualBox[54432]: 2 libdispatch.dylib 0x00007fff91646b26 dispatch_once_f + 117
02/05/2015 16:58:28.869 VirtualBox[54432]: 3 CarbonCore 0x00007fff87559456 _Gestalt_SystemVersion + 987
02/05/2015 16:58:28.869 VirtualBox[54432]: 4 CarbonCore 0x00007fff875586e3 Gestalt + 144
02/05/2015 16:58:28.869 VirtualBox[54432]: 5 QtCoreVBox 0x00000001024ad536 _Z8qWarningPKcz + 214
02/05/2015 16:58:28.869 VirtualBox[54432]: 6 ??? 0x00007fff653ecceb 0x0 + 140734892002539
02/05/2015 16:58:28.000 kernel[0]: VirtualBox (map: 0xffffff8023a3fd20) triggered DYLD shared region unnest for map: 0xffffff8023a3fd20, region 0x7fff8bc00000->0x7fff8be00000. While not abnormal for debuggers, this increases system memory footprint until the target exits.
02/05/2015 16:58:28.887 SIMBL Agent[1086]: #EasySIMBL add runningApp <NSRunningApplication: 0x7fbc7c317c30 (org.virtualbox.app.VirtualBox - 54432)>.
02/05/2015 16:58:29.659 SIMBL Agent[1086]: #EasySIMBL runningApp <NSRunningApplication: 0x7fbc7c317c30 (org.virtualbox.app.VirtualBox - 54432)> isFinishedLaunching.
02/05/2015 16:58:29.659 SIMBL Agent[1086]: #EasySIMBL VirtualBox started
02/05/2015 16:58:29.660 SIMBL Agent[1086]: #EasySIMBL app start notification: <NSRunningApplication: 0x7fbc7c317c30 (org.virtualbox.app.VirtualBox - 54432)>
02/05/2015 16:58:29.660 SIMBL Agent[1086]: #EasySIMBL checking bundle /Users/mike/Library/Application Support/SIMBL/Plugins/cDock.bundle
02/05/2015 16:58:29.661 SIMBL Agent[1086]: #EasySIMBL checking target identifier com.apple.dock
02/05/2015 16:58:29.661 SIMBL Agent[1086]: #EasySIMBL checking bundle /Users/mike/Library/Application Support/SIMBL/Plugins/ColorfulSidebar.bundle
02/05/2015 16:58:29.661 SIMBL Agent[1086]: #EasySIMBL checking target identifier com.apple.appkit.xpc.openAndSavePanelService
02/05/2015 16:58:29.662 SIMBL Agent[1086]: #EasySIMBL checking target identifier com.apple.security.pboxd
02/05/2015 16:58:29.662 SIMBL Agent[1086]: #EasySIMBL checking target identifier *
02/05/2015 16:58:29.662 SIMBL Agent[1086]: #EasySIMBL should install plugin /Users/mike/Library/Application Support/SIMBL/Plugins/ColorfulSidebar.bundle
02/05/2015 16:58:29.663 SIMBL Agent[1086]: #EasySIMBL send inject event
02/05/2015 16:58:29.664 SIMBL Agent[1086]: warning: failed to get scripting definition from /Applications/VirtualBox.app; it may not be scriptable.
02/05/2015 16:58:29.664 SIMBL Agent[1086]: AppleEvents: Send port for process has no send right, port=( port:27775/0x6c7f rcv:1,send:0,d:0 limit:5) (findOrCreate()/AEMachUtils.cp #526) com.apple.main-thread
02/05/2015 16:58:29.664 SIMBL Agent[1086]: AppleEvents: Send port for process has no send right, port=( port:27775/0x6c7f rcv:1,send:0,d:0 limit:5) (findOrCreate()/AEMachUtils.cp #526) com.apple.main-thread
02/05/2015 16:58:29.904 VirtualBox[54432]: Cannot find executable for CFBundle 0x10036d7c0 </Library/ScriptingAdditions/Adobe Unit Types.osax> (not loaded)
02/05/2015 16:58:30.255 VirtualBox[54432]: #EasySIMBL SIMBL loaded by path /Applications/VirtualBox.app <org.virtualbox.app.VirtualBox>
02/05/2015 16:58:30.255 VirtualBox[54432]: #EasySIMBL checking bundle /Users/mike/Library/Application Support/SIMBL/Plugins/cDock.bundle
02/05/2015 16:58:30.256 VirtualBox[54432]: #EasySIMBL checking target identifier com.apple.dock
02/05/2015 16:58:30.256 VirtualBox[54432]: #EasySIMBL checking bundle /Users/mike/Library/Application Support/SIMBL/Plugins/ColorfulSidebar.bundle
02/05/2015 16:58:30.257 VirtualBox[54432]: #EasySIMBL checking target identifier com.apple.appkit.xpc.openAndSavePanelService
02/05/2015 16:58:30.257 VirtualBox[54432]: #EasySIMBL checking target identifier com.apple.security.pboxd
02/05/2015 16:58:30.257 VirtualBox[54432]: #EasySIMBL checking target identifier *
02/05/2015 16:58:30.259 VirtualBox[54432]: #EasySIMBL loaded /Users/mike/Library/Application Support/SIMBL/Plugins/ColorfulSidebar.bundle
02/05/2015 16:58:30.260 SIMBL Agent[1086]: #EasySIMBL receiveSIMBLHasBeenLoadedNotification from org.virtualbox.app.VirtualBox
02/05/2015 16:58:35.000 kernel[0]: Sandbox: VirtualBox(54432) System Policy: deny file-write-unlink /Users/mike/Library/Saved Application State/org.virtualbox.app.VirtualBox.savedState/restorecount.plist
02/05/2015 16:59:50.934 SubmitDiagInfo[1007]: SubmitDiagInfo sucessfully uploaded 53 diagnostic messages
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Can't find an older version of VB to try out.

Try uninstalling EasySIMBL then reboot. I've been running 10.10.4 since the first developer seed with no issues.