The other day, a collegue brought to my attention that simply having Quick Tabs set in IE7 might cause CRM to hang.
Although I have not experienced this, I thought it would be helpful to others to get this out on our blog. You may be chasing the wrong rabbit trail -- as through debugging, you might be zeroing in on some jscript that might be triggering the problem; a plug in or something else totally unrelated.
If you're not sure if you have Quick Tabs set, your IE tabs will look like this:
This is a simple fix. To disable Quick Tabs, in IE, go to Tools->Internet Options->Tabs and simply uncheck Enable Quick Tabs, then restart Internet Explorer. CRM should no longer hang for you.