Fixed several conditions where VaultWiki wasn't able to generate thumbnails for large images. Your image-heavy pages should now send less data to the browser for most images. However, I still don't know if you were having trouble due to the images since you haven't said what page you were viewing when the browser crashed.
As I mentioned above, Firefox is not very good about memory use. It will keep consuming memory until the browser crashes. Even after that, you sometimes need to restart the computer to free the memory. This may give you the false impression that VaultWiki has caused the browser to crash. In reality, it doesn't matter what web sites you have open:
With Firebug / Developer Tools enabled on at least one tab, Firefox will drink up a few bytes of memory every second that you move the mouse cursor, even if you are moving it on a tab that doesn't have Firebug open. Closing Firebug stops new memory from getting consumed, but it doesn't free the eaten memory. If you have many tabs open, or Firefox has been open for a long time, the memory consumption can grow quickly.
In Firefox, viewing any page with a Flash element will cause the consumption to increase more quickly. Removing the Flash element via Firebug or closing the tabs that contain Flash do not free the memory either.
After Firefox has used so much memory, it is not available to other processes like Chrome or IE. If you use either one while Firefox is eating memory, or if there is not enough memory left after Firefox has crashed, they will probably crash too. This is at no fault of Chrome or IE or any of the pages you are viewing in those browsers.
These are just some behaviors I notice with Firefox on a daily basis.