I had an occasional annoying problem with Firefox: if I had a lot of tabs open and was scrolling around quickly in them, it would do the "severe error, please tell Microsoft" thing and crash. It did that three times in fairly quick succession last night, so I went a-googling.
Two answers:
First, make sure you have the latest Java cos one of the recent ones had a bug. I did have the latest Java, but also 11 earlier ones - apparently all the old ones stay in the machine, too. So I removed the lot. No improvement to Firefox crashing, but over a GB of disk space recovered, and the pooter seems faster, too.
Second, some users suggested the AVG8 Link Scanner causes this behaviour. I took the risk, and turned off the Link Scanner, and Firefox hasn't crashed since despite my trying hard to get it to do so. The AVG gets all shirty about this highly dangerous practice, so I've told Windoze to hide that particular icon.