Time Machine stuck on "Preparing backup" whenever returning from Boot Camp to OS X I have Windows 7 installed in Boot Camp. Whenever I go into Windows 7 and then go back to OS X Lion, and then run a Time Machine backup, Time Machine is stuck on the "Preparing Backup" stage for a long time (roughly 30 minutes). It usually takes 30 seconds in this stage in most cases.

The reason it's stuck at this stage is probably because it is re-indexing everything again (per this KB article), but the question is, is there a way to make it so that it does not have to re-index everything again after restarting out of Boot Camp? I think this only started happening in the past few weeks, while I've had Boot Camp installed on this computer for a few years now.
Okay so I figured this out a while ago, but I'll post it here too. The problem was I was using MacDrive, which allows me to read and write to Mac partitions while in Windows (using Boot Camp).

MacDrive sometimes modified files on the Mac partitions even if I didn't open them; I think it sometimes perform optimization actions to speed up the reading of Mac partitions.

This means that when I return to Mac OS X, Time Machine notices that a Mac partition was changed while outside of OS X, so it reindexes everything to be sure it doesn't miss anything.