What version of Moodle?
What does 'crash' look like? What happens? What happens if they use Firefox or Chrome? What version of IE are they using?
Version is Moodle 1.9
The crash manifests as the page becoming unresponsive and the mouse icon showing the egg timer as if it is trying to load something. We haven't tested in Chrome or Firefox, just in IE. IE is version 8.
So, that's the browser crashing rather than Moodle to be pedantic.
Please try with a different browser (Chrome or Firefox). You should also update IE to the latest version (9). If you are not using the standard theme then try it with that.
We need to eliminate the element that is causing the problem so, if you want it fixed, you will need to do a bit of experimenting