Javascript debugger unstable

Hi, I have a problem with the debugger regularly crashing the entire browser (all tabs freeze) and debugger breakpoints not stopping at the correct position. I use YUI and generally write classes to encapsulate functionality. I also have FireBug installed and while that doesn't have the same problems with debugger breakpoints, it does freeze the browser as often as the built in debugger does. I can't exactly pinpoint the problem. Alerts seem to cause this behaviour. I have Firefox 26.0 with the following Add-ons: Google Talk plugins Java applet Quicktime plugin Shockwave Flash 12.0.0.44 Silverlight 5.1.10411.0 The breakpoint problem always follows the same pattern. I put a breakpoint, reload the page and the debugger stops at the end of the class that contains the breakpoint and doesn't stop at the breakpoint itself. All of these problems don't occur using the Chrome debugger.