Most of the web pages for the sites I visit, where not opening on the first try or would not finish loading, if they started to load at all. Had to press re-load to force the web page to fully load or complete loading.
Overall made the browser work slower.
Disabling added plug-ins one at a time found that the Adobe Acrobat 184.108.40.206 plug-in is the culprit. Disabled it and Firefox 3.6.6 completes loading web pages as fast as it should.
Just informing forum users in case they are experiencing same or similar problem.