hmm, strange problem. you could have some infected cookies or a virus your av hasn't found
if you have a flash drive you can transfer these to from the working computer to the
problemed computer:
try running
SUPERantispyware &
Malwarebytes Anti-Malwareand after the scans,
Download
HijackThis.exe (HJT)
* Double-click on HJTInstall.
* Click on the Install button.
* It will automatically place HJT in C:\Program Files\TrendMicro\HijackThis\HijackThis.exe.
* Upon install, HijackThis should open for you.
* From the desktop open HijackThis.
*
If using Windows Vista, Right-click and Run As Administrator.* Click on the Do a system scan and save a log file button
* HijackThis will scan and then a log will open in notepad.
* Copy and Paste the entire contents of the log in your post.