ACPI Lid wakes computer every 3 minutes

My Dell Latitude e6500 has been running great under w7 for several weeks. However, recently, it has been waking up from sleep every time I put it in. Checking the event viewer, I found something disturbing. Under "Power-Troubleshooter," there were many consecutive Event ID 1, stating:

Now, the weird part is that there is one of these events exactly every 3 minutes! (e.g. 12:03:35pm, 12:06:35pm, 12:09:35pm, 12:12:35pm, etc.)
This occurs is while the lid is securely shut or wide open, sitting on a desk or in its sleeve, plugged and unplugged.

Also, running powercfg from an admin command prompt does not let me disable "ACPI Lid"... it says I do not have permission!

Any ideas on why this is happening?

I have found the culprit... it seems that a registry hack i did "HKLM\SYSTEM\CurrentControlSet\Control\TimeZoneInformation\RealTimeIsUniversal" to set the Real Time Clock to UTC ... so Windows and Mac OS X don't screw each other's clocks up (dual-boot with OSx86) had caused this. Disabling that DWORD fixed the sleep problem. I guess I'll just have to deal with changing the clocks manually whenever i use OSX.