Your computer may not be as clean as you suspect it might be.
The Heur Trojan is one Trojan that tries to hide its self by creating new varients of its self by changing its name to avoid detection.
Read this article. http://www.ehow.com/way_5762738_heur-trojan-removal.html
•Slow Internet browsing, a different browser homepage, Windows instability, modified desktop wallpaper and fake Dr. Watson security alerts are all symptoms of a Heur Trojan infection. You can verify that your computer is infected by installing anti-virus software. Perform a complete system scan, and it will indicate the presence of this virus by displaying "Generic.Trojan.Heur", or some variation of those words
•The Heur Trojan is a polymorphic virus consisting of multiple files, which means it is constantly changing to avoid detection and removal. This also means that no two copies of the malicious files are exactly the same, and can sometimes make removal difficult.
The first step to combating this infection is to install AVG's free anti-virus program. Download it (see Resources for a link) from the AVG homepage and install it, then click "Update now" to ensure you are using the latest AVG virus definitions. Select the "Computer Scanner" tab and then click on the "Scan Whole Computer" button. The time it takes to scan your entire system depends on how fast your computer is, and how much data is stored on your hard drive. After scanning, the anti-virus software will display a list of files that are infected; these files comprise the Heur Trojan virus. Select the option to "Move to Vault," and the files will be quarantined and prevented from executing. Reboot your computer and again perform an entire system scan with AVG's anti-virus program. If the second scan shows no signs of infection, then the Heur Trojan was successfully removed. If the Heur Trojan is still present, you will have to attempt to remove it using a more specialized type of anti-virus software.http://www.avg.com/us-en/homepage
You can also try Mawarebytes Anti malware http://www.malwarebytes.org/
Download the Free version, update it and scan your computer.
Edited by MrBruce1959, 15 September 2010 - 03:56 PM.