Hello - I think, as many others have encountered, that Firefox 4.0.1 has a memory leak issue. I found this when working with the jQuery library's ajax functions, and I created a simple test case. I've outlined this in detail here: [http://forum.jquery.com/topic/memory-leak-with-jquery-1-6-1-and-firefox-4-0-1 http://forum.jquery.com/topic/memory-leak-with-jquery-1-6-1-and-firefox-4-0-1]. Basically, the sample I created loads jQuery from Google's API CDN, creates a function that makes a simple ajax request (and does nothing else), then sets an interval that runs the function once every second. The net result (over a long enough period of time) is that no additional memory should be required after this function has run more than once. If I monitor the memory used by Firefox, after about 5 minutes there is a clear and consistent trend of memory usage increasing, with no end in sight (note that within the first 5 minutes, the memory may decrease initially...but that's not a long term trend). I can reproduce this problem 100% of the time with Firefox, in safe mode, on both WinXP and Linux. I cannot reproduce the same problem with any other browser. So...is this a bug? I've been searching various sources, and I cannot find a definite answer. Since this is only happening with Firefox, then it seems to me that this is where the problem lies.