My company has acquired a new client for tech support. I went there to install antivirus on their workstations as we do for all our clients. This new client has Win7 on all workstations and a small business server running in a domain environment.
I installed Kaspersky on all 8 pc's in their business. The next day we got a call from one of them saying their computer was acting strange. Once I got there I discovered the pc would freeze when launching Quickbooks or Outlook. I ran a malware scan which turned up nothing. Then after some troublshooting steps I decide to uninstall Kaspersky. Well what do you know, that worked. I didn't want to leave him with no protection so I installed AVG free. Same outcome. The computer only will operate without antivirus.
Is this happening before or after an initial full scan of the system by the AV app? Many AV apps do a sort of baseline "full" system scan after installation. Then, they only looked at changed files afterward (performance increase method).
When you install Kaspersky or AVG, they usually perform a full scan upon restart. That scan can take quite some time (depending on the system in question). So, was this a one time event or every time the system restarted (after the initial scan was completed)?