First of I'd like to state that I know this will be difficult to find as the bug is reproducible only on certain machines running IE6. I only found it because I wrote a javascript error reporting tool into our web app, and tracked this bug down to specific lines of code. Out of thousands of users only dozens have experienced the bug, always with IE6, and possibly only after the update to jQuery 1.4

The bug is as follows, a jQuery select such as $(".bodyDiv") will return a null object. Changing the class selector to an id selector such as $("#bodyDivId") eliminates the problem.

Solutions I've tried that have failed are: delaying execution by 400ms

Solutions I will try is using this fugly selector:

$("[class*=className]")

and trying to roll back to jQuery 1.3 (which is clearly suboptimal)

Once again, I know this will be hard to fix because it's difficult to reproduce (I could not on out IE6 installation) but if someone can try to figure out how this can happen (tracking how the null object is being returned is probably the most likely way to find the problem), and if not fixing it, maybe at least fallback to selecting it using the fugly selector above, I would be eternally grateful.

If there are any question or possible solutions I can try out I'm more than willing to help.