I was trying to use Microsoft Visio 2007 inside a Virtualbox Windows VM. For some reason, though, the VM would crash immediately after starting Visio.
Microsoft Word: fine. Microsoft Excel: fine. Microsoft Visio: crash.
Turns out this is actually a documented bug with the Virtualbox Guest Extensions, of all things. Versions of the guest extensions between 4.0.0 and 4.0.4 just don’t like Visio.
The solution is either to upgrade to a newer version of the guest drivers (4.0.5, a development version) or downgrade to the 3.x series of guest drivers. I did the latter and Visio now works fine.