I just got my iMac back from the Apple Store; they replaced some bad RAM. They wiped the hard drive, and so when I plugged in my TM drive, it asked if I wanted to use it for TM, so I (of course) told it yes. All of my old backups then showed up in the TM browser, but now, after migrating my old account from my TM backup, all I have is a backup from yesterday appearing; it won't back up any more data because it says it's out of room (apparently, it's trying to do a complete backup). How do I get it to see the old backups and start doing incremental (or whatever!) backups again?