I have a Kaspersky Anti-Virus 6.0 for Windows Workstations v. 6.0.3.x, and the license is for 10 PCs. I installed it on Windows XP based machines and all of them work fine. Got only one PC with Windows 7. I receive an error message on that PC: Protection components failed to start.
Update to version 220.127.116.114.
I use it at work under Windows 7 x64 with no issues so far.
Have a look here:
It is officially compatible with Windows 7.
Kaspersky Anti-Virus 6.0 isn't compatible with Windows 7 - you need to upgrade Kaspersky