Well, it wasn't the CCCP. It ran well for a while then occasional crashing started again. I gave up for the day.
Today, I switched the PC on, started MC, moved to recently imported, right click>locate artist>back - crash.
Restarted MC, recently imported, right click>locate artist - crash.
I then remembered I have a second PC with MC12, 301 on that I don't use much and just contains some backed up stuff. I went to the video library on it and selected locate artist then back button and... crash. The instruction at blah blah blah.
Basically, the only thing these two PCs have in common is they are WinXP Pro SP2. Neither MCs are using any 3rd party apps. Although I've messed around with some codecs on the first PC, I haven't touched the codecs on the second for ages, apart from updating DivX. I've just checked and it appears I don't even have DivX on the first machine.
Any ideas? In the meantime I'm going to update the first machine to 308 and see if it makes a difference. Come to think of it, although I'm not sure, this crashing problem could have started with 301. I was in the 290s for a long time without any problems.