Firefox and Firebug

Installed Firebug the other day.  Probably no need for most of you do have it.  It's a web dev geek tool.  Anyway, just in case, I've been noticing Firefox dragging and gradually getting worse.  Did a little checking and at idle Firefox was consuming 25% of my CPU.  Tried to quit and it shot up above 100% (dual proc machine).  I didn't wait around to see if it would eventually cut loose and killed the process instead. 

Not positive it's Firebug but Firefox has been rock solid for me for ages.  Timing is suspicious.  Might be worth keeping away from that particular add-on. 

Thanks.  If it did that to your comp and you're on a dual proc, I can't imagine what it would do to ours (one that isn't).