The F-Prot 3.x uninstaller of the Windows version has apparently a glitch. Due to how Windows works, this may lead to a blue screen if the driver entry in the registry was not removed during an upgrade to version 6.x! To mitigate this issue until the next version is released, use the fix described here before you reboot the system after upgrading from F-Prot 3.x to 6.x!
// Oliver
PS: The next release of the 6.x installer will be aware of the issue and incorporate the fix.