Hi leguygt,

Have you looked at our performance troubleshooting section? There is a lot of good information in there that should help.

Hopefully this helps!

Help > About Firefox = try to force another update

Many days there's more than one update version generated and the afternoon version usually corrects faults in the morning version. Sometimes though it might not be fixed until the following day. Ah, the joys of living on the cutting edge of development.

I do manual updates for Aurora and Nightly, and wait until the evening (UTC -6) to update them both.

See also http://ftp.mozilla.org/pub/mozilla.org/firefox/nightly/latest-mozilla-central/

Yes, I have looked and I'm still looking through the "performance troubleshooting section" and have followed most of the suggestions but incorporating the suggestions have yet to resolve the issue. Prior CPU Usage would occasionally jump above the 75% level for perhaps 30 seconds or so but it would always drop below the 30% mark in short order. As indicated in the problem description... with or without Firefox running... my CPU now runs in excess of 50% all the time and never dips below 50%. Running in Safe Mode has no effect of reducing CPU Usage.

Just ran an update [13.0a1 (2012-03-01)] 15-min ago... no change. CPU Usage still hasn't dropped below 50%. Disabled hardware acceleration everywhere I'm aware of. No effect as yet.

Searched with keywords "CPU Usage" and excessive idle. Found the following link

http://answers.microsoft.com/en-us/windows/forum/windows_7-performance/presentationfontcacheexe-uses-50-of-my-cpu/4200fe85-458f-4f19-b791-1fe5395304da

Followed the instructions and it worked like a charm. CPU now idling between 4% and 12%. Sweet!!

open local c and search type fontcache then delete fontcache3.0.0.0.0 and fontcache 4.0.0.0.0 then empty rubished bin then reboot. fix