??  which ff ARE YOU USING??  3 IS still BETA.

I'm using the latest stable version.

I've used Task Manager to see what else might be hogging CPU cycles, but it's usually just FF spiking on its own.  I may try running it with all the plugins removed, then add them back in one at a time.

Are you using a wireless or USB keyboard rather than wired?

Does the delay occur when you have only 1 tab open (like CM)?

Are you running dual monitors?

Do you have any Symantec (Norton) or McAfee products installed?

Are you hardwired to a NAT router?

You mentioned XPSP2.  Do you have all the latest updates?

Did you install IE7?

lONG DISTANCE COMPUTER REPAIR IS anythinG OUT OF HANDS REACH..
Its a pain and hassle to TRY to get someone to do 1 thing, Explain it, when you could have dont 10-100 Analysis in LESS time.

Need to know Whats running in the background,
What Anti virus and Bot protection you are running..
Need to know HARDWARE on machine..DELL, HP, Model, CPU, RAM, HD space available, Video card and ram.

what is the connection to the NET, and ISP..  USB,NIC,Dialup, 56k, 256k,1mb,???
Anything WIRELESS...(real bung hole can happen here, as well as INTERFERENCE from other devices.)

Its fun aint it...
I WILL NEVER use Norton or McAfee again..they use to be GOOD..If you REMOVED these programs, DID you get ALL of them..

What have you INSTALLED or REMOVED recently...Last month should do.
Any Program testing??  Any LARGE programs?

I'm not that trusting. If you want to go down that path, I'd suggest a fresh FF install, preferably in a new directory.

This really isn't worth having you guys waste troubleshooting time on.  It's been laggy and draggy for a long time now, probably since 1.5 came out, and I've just had to live with it.  I even had to dump an install once and put a fresh copy on.   I just have to live with it, and use Opera more frequently.

I know it's FF causing the issue, not my computer--why does everything BUT FF run well?  (Even if I edit a big honkin' Photoshop file or WAV file in Sound Forge, my computer never shows any slowdowns.)  The memory leak is a well-known bug in FF that still hasn't been fixed.  In fact, it occured to me that it's after FF has run awhile that it gets sluggish.  I just started it fresh this morning (about a dozen tabs) and I'm getting few, if any, lags now.  My computer's on 24/7, so it is not uncommon for me to have FF open for a few days in a row, with many tabs and a couple of windows open. 

That's the ticket right there.  More than 1 firefox window open for more than 1 day is the perfect recipe for disaster.  Problem solved.

Heck, I've left other programs open for a week or two (Photoshop, which I always leave open since I often need to quickly knock out a graphic for a site I'm working on...or CuteFTP to upload files to one of the servers), and they show no ill effects.  A couple of other program I use get dicey when left open, like Topstyle Pro (a CSS editor).  Heck, I've had Opera and IE windows open for days with no ill effect.  Maybe I'm just asking too much.  But hey, the price was right. 

I'm glad FF has the option to open up your previous session, since I've often dug things out of search that I don't want to hunt for again...

Rudy,
you are talking about an OS that has had holes in it for years, Written in a Language, WRITTEN by the same corp, and the ONLY group that knows HOW either works, WROTE both, and hasnt fixed Anything.(not very well, anyway).
So that Anyone writing a Prog for MS, STILL cant make things always MESH well.

And this is the only problem you have with it??!!? You're doing great. I'd never leave windows running for a week. I hard boot the OS daily. Of course, that's 'cause I don't like to waste power and don't want my work laptop on and hot on my back while riding my bike.

Still though, even when I didn't care so much about power and only turned off the monitor on a desktop, I always booted at least every few days, or possibly once a week at the longest, but knew I was taking my chances.

What do you think you're running? A real OS? It's from PicoFlaccid for FSM's sake.

Apparently so!    I actually don't reboot unless there's an update I need to apply...it runs fine no matter how long I let it ride.  I've had it booted for a month a couple of times, and it's worked as smoothly as if I'd just booted it up.

I'm not for/against any particular OS...to me it's just a tool, and it works.  I can get my daily work done with no problems whatsoever, and I have too much tied up in software to jump ship anyway. 

Add adobe flash swf browser crasher. Also look for a google software update demon in task list. took three different places to kill it off. It reloads automatically unless both the plist & app are removed. look in ~/library & /system/library &  /library & any preferences. BOTH Safari and FF 3.0.8 got better. Keystroke lag gone in safari and reduced in FF3

FYI

A common happening with Firefox. I find it only happens on pages with Flash enables ( via Noscipt) so the most likely culprit is Flash player plugin. It only really started happening with newer versions of the player, and will hog CPU for up to 2 minuted until some internal timer expires, then fine for hours. I just use it as a reason to get up and walk around, come back just now.