I suffered the same problem but it disappeared. Possible reason here. Anyone has the same situation? Please give me some feedback if it's correct.

Running OS 10.6.7 plus last Firefox before 4.0. Reluctant to move to 4.0 as it is still new.

This is a new problem, beginning in the last month or so for me, I think. While it seems much longer, I believe the delay is about 20 seconds, and it does happen every time Firefox launches.

Further, sometimes (do not yet see a pattern) well after launch, when attempting to navigate on a website...Firefox isn't paying attention. I think the interruption may be 20 seconds here, as well. Then all is well.

No magic living color pinwheel displayed by uncle Mac during either delay.

Did I mention table pounding frustration when on deadline?

Got a similar issue, except I get the spinning wait cursor for approx. 30 seconds, after a random action, like opening a new tab window, or maybe a link? I have an acute awareness of computer issues, but this one is so baffling that it's hard to put together a succinct google search term in the hopes of finding the answer!

The [Hangs] support page has so many possible causes that it's not much help!! And the problem is that it might only happen a couple of times a day from a full day's worth of browsing - so it's so hard to troubleshoot!

Will try qingbo's solution, and will post if I somehow catch the culprit. I'm running Firefox 7.0.1, but it's happened during the last few major versions of Firefox.

-> Clear Cookies & Cache

• https://support.mozilla.com/en-US/kb/Template:clearCookiesCache

-> Clear the Network Cache

-> Reload web page(s) and bypass the cache.

• Press and hold Shift and left-click the Reload button.
• Press "Ctrl + F5" or press "Ctrl + Shift + R" (Windows,Linux)
• Press "Cmd + Shift + R" (MAC)

Check and tell if its working.