So I got into this neat state where anytime I clicked a shortcut to a program on my Start menu, Windows Explorer crashed. This was, as you might expect, getting pretty obnoxious. I uninstalled the program that I thought was the most likely candidate, as I had updated it yesterday, and it's just the sort of thing that would crash Explorer. After restarting and confirming that that program no longer existed, I was still getting the crashes.
Luckily, I had the Visual Studio handy. So, I attached to the process, clicked a shortcut, and then Explorer crashed as expected, but this time the debugger caught it. I looked in the callstack, and everything looked normal except for a DLL that didn't look like it should be there, cmdlineext.dll. So, I did a web search. It turns out that it's a part of SecuROM, Sony's constantly-maligned and dubiously legal copy protection software. (I don't know if there could possibly be a program that the world hates more than SecuROM. Probably not even RealPlayer.)
So, I shut down Explorer, unregistered and deleted that file from a command prompt, and then restarted Explorer. Tada. No more crashes. Took about three minutes to diagnose and fix. Sometimes it's handy to be a software developer and have a debugger handy.
I hate Sony more with every passing day. It takes a lot for me to have actual negative emotions upon the mere mention of a company's name, but Sony certainly manages it.