We now need to make certain that this issue is not malware because if we troubleshoot otherwize we may be wasting our time.
Please go to the malware forum and follow the instructions at the top....Especially the Instructions things to do before posting in the malware fourm.
That will give you several steps that will help you clean up 70 percent of all problems by yourself. If at the end of the process you are still having difficulty--and you may not be-- then post a hijackthis log in THAT forum.
If you are still having problems after getting a clean bill of health from the malware expert, please return to this thread.