It may be also a sign of some infection.
With the information you have provided I believe you will need help from the malware removal team. I would like you to start a new thread and post a DDS log HERE
and include a link to this thread. Please make sure that you read the information about getting started
before you start your thread.
It would be helpful if you post a note here once you have completed the steps in the guide and have started your topic in malware removal. Good luck and be patient. Help is on the way!