This morning, I woke up to find my new Dell E1505 laptop freaking out (new processes would start, but their windows would never display - usually followed by complete system lockup.) Hard restarts produced the same symptoms on startup. A new laptop - less than 2 weeks old - already completely hosed. I am not pleased.
On one restart I noticed some error messages indicating a null reference exception in unmanaged code (gee, that's helpful) so I took a look in the event viewer for more information:

Faulting application svchost.exe, version 5.1.2600.2180, faulting module msi.dll, version 3.1.4000.2435, fault address 0x00012780.
Interesting - seems like something is trying to install/uninstall? I couldn't remember do either recently (well, the day before anyway) so I turned to Google. The second hit in my
search results was a
blog entry by Scott Swigart about my very problem. About 2 minutes later, problem solved. Thanks Scott!