Didn't solve it, but thanks. Reading some other related threads, one said to uninstall then reinstall Shockwave, but that didn't remedy it. Another suggested it could be a sign of a failing HDD. I have noticed it seems very hot lately where the drive is (it's a laptop), so I'm considering putting in a new one (it's only an almost full 40Gb so a larger one would be welcome). What's the recommended (free?) program to clone the drive, EASEUS Todo Backup Home?

Well I took the easy option - stopped using the XP laptop and used another one (Vista) and now (4 weeks later) the same thing happens with that one: browsers crash or freeze - except Chrome - but also when I tried to run AVG the interface wouldn't open. Eventually I removed AVG but couldn't re-install it (or Avast) but did manage to install MSE. Did a scan which came up clean but now any program I try to install won't complete. I also want to uninstall then re-install Flash but every time I run the uninstaller (having exited all running programs) and restart the machine it still reports I have flash v.10 installed. Oh, and I tried the XP laptop and it appears to be working fine again???