I am running Zone Labs Internet Security Suite antivirus and anti spyware

I am running Smart Address For the last two or three weeks (September to October 2009), the anti spyware scan picks up a file C:\Windows\System32\isxdll.dll and claims it is infected with the trojan Win32.BackDoor.Graybird.

Deleting isxdll.dll stops Smart Address from running. So then I need to reinstall Smart Address which replaces file isxdll.dll which then triggers Zone Labs Internet Security Suite anti spyware on the next scan.

Has anyone else had this problem?

Can anyone explain what could be happening here?

Should I be worrying?

Is this likely to be a Smart Address problem or a Zone Labs problem?