I've got a rig with 2 hard drives. I've put Ubuntu 9.04 (Jaunty) on one of the drives and Windows Vista SP2 runs on the other drive. I went with this approach rather than dual boot since I wanted to be able to swap out the OSes as I please and just keep things clean and separate.
The problem I've been noticing is that when I am in Ubuntu and I reboot into Windows Vista (by selecting the Vista drive at boot time), the Vista clock is always set back by about 5 hours. Also I've noticed that when I try to synchronize the Vista clock, it always errors out on the first attempt, then I have to click "Update now" a second time before the synchronization with the selected NTP server takes effect. Repeated reboots of Vista do not affect the Vista clock so long as I go from Vista back to Vista each time.
Also, the reverse is not true, that is, rebooting Vista and launching Ubuntu does not affect the Ubuntu clock.
I can't figure out why this is happening. Would appreciate any help at all.
Update: I should also probably mention that Ubunty is 64-bit and Vista is 32-bit.