Periodically I notice Firefox getting slower and slower (e.g., scrolling gets jerky) and consuming a lot of memory (up to 2GB). If I File -> Exit from Firefox and watch the processes in the Windows Task Manager, I sometimes (but not always) see that a Firefox process continues to run and its memory has not been freed. After several minutes, the process still shows no sign of going away. If I manually end the process and restart Firefox, it performs well -- until it begins slowing down again.