You can try what crazyman suggests but it is more than likely conflicting with another utillity for spyware/malware that you have installed. Norton and Mcafee both don't like other programs using the same DLL files as they do and will act up till you uninstall the other programs.
This new symantec product is a real bug. Did you purchase it? Anyway, try installing other anti-virus such as AVG <it is freely available> or if you want to spend another money, try McAfee - this is one of the best anti-virus so far.