I'm afraid you haven't provided us with quite enough information to be able to do anything about the problems you've reported.
First of all if something isn't working in the browser, could you check for browser errors and let us know if anything came up there?
Secondly, if events do not work in general, could you make a simple one-event project and upload the .capx file? This will help us see if you've done anything differently which might be breaking it.
Finally, I'm afraid if Firefox crashes that's a problem with Firefox and we can't do anything about it - you'll need to report the problem to Mozilla. Have you tried Chrome by any chance?