Windows 7 guest on OSX 10.7.5 host fails

[carnun]

Over the last day I am unable to startup my Windows guest that I have been using for a long time. Originally it failed on VirtualBox 4.2.6, but now I have upgraded ro 4.2.8 and it still aborts. The error message is copied below. I have tried enabling and disabling 3D acceleration as some of the forums suggest that is a workaround but have had no success. The only major upgrade I done over the last week is to move to the latest Java version for OSX. I need to use this VM to perform work so this is becoming a serious issue to me.

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Failed to open a session for the virtual machine DemoWin7x64.

No error info.

Result Code: NS_ERROR_CALL_FAILED (0x800706BE) Component: ProgressProxy Interface: IProgress {c20238e4-3221-4d3f-8891-81ce92d9f913} ---

[carnun]

Note that I have a Linix based file server that successfully runs on the same Guest OS.

[carnun]

I have now successfully started the Windows VM, the only change being that I stopped the application called HandBrake that was running in parallel on my OSX Guest OS. Handbrake was backing up DVDs to my hard drive and carrying quite a high CPU load....