Windows 7 - Firefox Slow to Operate???

I've noticed a huge decrease in the performance of Firefox. I know that people are experiencing crashes and what-not, which I (knock on wood) have not yet. But I have definitely experienced a major decrease in speed, to start up and loading between pages.

Are there known issues with Firefox? I never had issues with Firefox in Vistax64. Any ideas?

I am not having any issues on Win 7 32 bit. It is snappy.

Have you upgraded to Firefox 3.5.4?

Do you have a bunch of extensions and how does it perform with the extensions turned off?

Yeah I have 3.5.4 and I have no extensions on there (just did a clean install as I got Windows 7 last week). So I am unsure what else is going on...

One thing I have noticed on Vista and once on Win 7:

I am viewing a web page. I shut Firefox down with the red X at the upper right.

A few minutes later, I poke the Firefox icon to restart the browser.

Nothing happens other than an error message to the effect that Firefox is already running, even though I see nothing on screen.

I look in task manager and see that Firefox in fact is running and is occupying 50% of my CPU cycles. I have to shut it down in the task manager before I can actually open it on screen.

This happens intermittently and may be rarer in Windows 7, but it is annoying.