After closing Firefox 3.5.3, firefox.exe keeps running

Name:    
Product: Firefox
Summary: After closing Firefox 3.5.3, firefox.exe keeps running

Comments: 
After closing Firefox 3.5.3 by clicking X, firefox.exe keeps running for
minutes, with spikes of high CPU usage.

This issue is terribly common. Happens 8-9 out of 10 times and has been
present since Firefox 3.5.0.

Browser Details: Mozilla/5.0 (Windows; U; Windows NT 5.****-US; rv:1.9.1.3) Gecko/20090824 Firefox/3.5.3 GTB5
From URL: http://hendrix.mozilla.org/

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