It sounds like you have an infection and you should probably take this over to the "Am I infected? What do I do" forum. Have you ran any scans to determine if you have been infected if not you can run the one below.
Hi please try going here http://www.eset.com/us/online-scanner/
for a scan.It's best if ran in IE you can run it in firefox however there is one extra step involved. You will need to disable your current installed Anti-Virus
When prompted allow the Add-On/Active X to install.
Make sure that the option Remove found threats and the option Scan archives are checked.
Now click on Advanced Settings and select the following:
Enable Anti-Stealth Technology
Now click on:START
The virus signature database... will begin to download. Be patient this may take some time depending on the speed of your Internet Connection.
When completed the Online Scan will begin automatically.
Do not touch either the Mouse or keyboard during the scan otherwise it may stall.
When the scan completes, press the LIST OF THREATS FOUND button
You can delete what was found (if given the option choose "quarantine" instead of delete"
When completed select Uninstall application on close if you so wish, make sure you copy the logfile first!
Now click on: FINISH
Do not forget to re-enable your Anti-Virus application after running the above scan!