Try this steps
1.- Clean the recent history in your browser, navigation cache, cookies, sessions, searches
2.- Disable the addons that you don't use usually or the ones you set recently, a lot of them make your browser works slower and others cause conflicts (like real player addons)
3.- Clean the registry with free tool like ccleaner, regseeker or both
4.- Scan deep your pc with an antivirus (nod32 or other you've got) and malware (malwarebits antimalware)
5.- Install an antispy and keep it resident (I recommend spybot S&D)
most complete tool, (if you have much ram), Zonealarm Extreme Security, it's antivirus, antispy, mail protect, firewall, etc
6.- If you want to keep clean your machine without worrying (you can use Tuneup Utilities, It does machine maintenance automatically for you )
I hope you solve the problem
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