well, the good news is that I doubt you have a hardware issue, because if it was the RTC, the bios would be off as well. The bad news is that something that is running on your system is causing your clock to lose time, the question is what application or service is doing so? I would start with disabling al the time synching that is currently enabled. Then, see what services are running that are not part of the OS and stop/disable as many of those that you dont need to see if the drift stops. you can also try this program (if permitted) called Clock Watch Server, and you can configure it to show the system time and the bios time simultaneously www.beaglesoft.com/CWFileXfer.htm
We use this on occasion to see if any of our apps care causing time drift. once its installed, click options, then BIOS clock, then put a check in the Enable BIOS clock as time base box, then click Test.