I have had ongoing problems with TM since installing a new HDD in late May. The problems have been varied, and for a while all backups were taking about 2 hours. Now things have "stabilized" and backups take between 15 and 20 minutes, tending towards the latter.
TM always runs two loops according to each backup log, which creates two files each time. Assume the time is 10:35-ish a.m., and I will have one as "in progress" with a time stamp of, say, 10:25 a.m., and a "completed" with a time stamp of 10:30 a.m. That is not a typo - the "in progress" is always older than what is listed as the most recent backup. I'm out of troubleshooting ideas, including zeroing out my TM drive, losing lots of precious backups.
I have read Pondini's excellent site exhaustively, and am at my wit's end. I am about to reinstall 10.6 at this point, but would rather not.
Hardware: late 2008 MBP running 10.6.8, WD My Passport Elite 500 GB External