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Recently FireFox often has been causing 100% CPU usage and locks up until it finishes the process (various ones). Clearing cookies/cache didn't help. Any ideas?

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New Contributor

Recently FireFox often has been causing 100% CPU usage and locks up until it finishes the process (various ones). Clearing cookies/cache didn't help. Any ideas?

Windows 2000 SP4, 1g RAM, Firefox 9.0.1 We keep IE6 and Firefox open simultaneously for 2 different mail accounts. Firefox was always much faster even with 3 or 4 tabs open, but for the past couple of weeks when trying to update a screen the CPU suddenly goes to 100% usage and of course nothing will move until the particular process is finished. Closing one or more tabs does not help. If I close Firefox completely with Task Manager CPU usage goes back down to nil. After restarting Firefox CPU usage may or may not go back up depending upon whether it tries to continue the previous task that was locking it up. It did not do this with Firefox 3.6 but then again it didn't happen immediately after updating to 9.0.1 either.

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Shooting Star Contributor

Re: Recently FireFox often has been causing 100% CPU usage and locks up until it finishes the process (various ones). Clearing cookies/cache didn't help. Any ideas?

Hi vbolton,

Have you looked at the Knowledge Base article Firefox uses too much memory (RAM) - How to fix or Firefox uses too many CPU resources - How to fix? There is a lot of great information in there.

Hopefully this helps!

3 REPLIES
Shooting Star Contributor

Re: Recently FireFox often has been causing 100% CPU usage and locks up until it finishes the process (various ones). Clearing cookies/cache didn't help. Any ideas?

Hi vbolton,

Have you looked at the Knowledge Base article Firefox uses too much memory (RAM) - How to fix or Firefox uses too many CPU resources - How to fix? There is a lot of great information in there.

Hopefully this helps!

New Contributor

Re: Recently FireFox often has been causing 100% CPU usage and locks up until it finishes the process (various ones). Clearing cookies/cache didn't help. Any ideas?

Thanks very much Matt! Those articles sound very helpful - I guess I didn't look hard enough to find them. Will try them tonight after my getting-rid-of-old-junk-computers binge to free up workbench space for a suitable test computer. Vic

New Contributor

Re: Recently FireFox often has been causing 100% CPU usage and locks up until it finishes the process (various ones). Clearing cookies/cache didn't help. Any ideas?

100% CPU usage occurred most often toward the end of the working day when busy trying to print on-line postage. We don't have any memory-consuming plugins but according to the knowledge base articles Firefox memory usage can gradually increase during the day even if you do nothing. It seems that may be the problem so we close and restart Firefox more often now as that usually fixes the problem. However, if we get stuck on a particular website update that causes the CPU to to go 100%, we can always start Firefox without previous tabs so the update will stop, or simply use a different browser until we have time to let the computer play games with itself. So our workaround of restarting Firefox turns out to be the final solution (until we find something better - will post it if we do). Vic