blue box during app install in virtualbox?!?

[Beowulf.1000]

Need help! Trying to install Sibelius 6 (music composition software) in Windows XP running in Sun/Oracle PUSE Virtualbox. When I start the install, all I see is a blue box are where one would normally see the app's install choices (click here to install, etc). I was able to install this software perfectly months ago, same WinXP, same Sibelius, so something is fowling this all up.

What has changed? I upgraded my quadcore cpu to a six core. I was running Ubuntu 9.10 i386 but just installed off CD (fresh install, not upgrade) Ubuntu amd64 10.4. I suspect the version of PUSE virtualbox is a newer version compared to a few months ago. Upgraded from 20 inch 1600x900 Acer LCD monitor to 1920x1080 Acer LCD monitor. New Ubuntu install was done just yesterday, so after the cpu and LCD monitor upgrade. My system has 8GB of RAM.

I really wish I could get that Sibelius installed and running, because it installed and ran beautifully before. Now I am frozen out of an install, just a navy blue box on the WindowsXP screen where I should see the Sibelius install screen information.

Same nvidia graphics card (GT 7900), Ubuntu nvidia proprietary graphics driver. 2D and 3D acceleration enabled in virtualbox.

Help? Ideas?

[Beowulf.1000]

No takers? Sigh. Well this just shows why the mantra 'Just use virtualized Windows' does not cut it for replacing Windows. Once again I guess I will be disconnecting my extra drive with Ubuntu on it, just stick with Windows 7 for now. Too many software programs for music composition like Sibelius, KOMPLETE 6, that just need native Windows and have no adequate comparable replacement in linux.

Even more disconcerting to me is the fact that Sibelius 6 installed and ran perfecting in virtual box just a few months ago, with the previous version of virtualbox that I had installed in Ubuntu 9.04, but now does not install. This is disturbing, because one can not count on Windows software installed in virtualbox continuing to run in the future give the changing nature of versions of virtualbox and ubuntu that history has now show can stop the software from installing and working.

I really have wanted to switch to linux, but alas for my software needs it just is not viable.