What is the screensaver you are using? Try to give exact steps to reproduce the problem, someone may be interested and have an answer.

"What is the screensaver you are using?"

The built-in screensaver with XP.

"Try to give exact steps to reproduce the problem, someone may be interested and have an answer."

Open Firefox, run the screensaver, enjoy all the freeziness.

Not sure what you are running, consider not running it ?

Are you able to give details of the process/program that you run that then causes problems with firefox ?

Not sure what the mystery is here. If I leave Firefox open and my laptop alone long enough for the screensaver to come up, Firefox will freeze after I clear the screensaver. Guaranteed, 100% of the time.

Please be specific about what other information you need.

As a workaround do not use the screensaver, or close firefox when not in use. Obviously firefox should not be freezing after a screensaver runs. Does firefox freeze after a long time even if the screensaver does not run.

One problem of firefox hangs with a workaround is discussed in: http://blog.bonardo.net/2011/09/30/is-your-firefor-freezing-at-regular-intervals