Initial Backups Failing

Question

I've tried to research the answer to this problem, but have found only advice for people who have had Time Machine work correctly for them before, and suddenly stop backing up correctly after a while.
+My problem is that Time Machine will not complete the initial backup.+ When I set it to backup from my MacBook Pro running 10.5.5 (just upgraded from Tiger a week ago, woo-hoo!) to my FireWire 500GB WD drive, the backup starts correctly. All is fine until it gets to a certain point, typically in the 6-10 GB area of backing up (that is, after backing up about 6-10 GB of data). At that point, an error message pops up, saying the backup could not be completed. If I tell it to do it again, it might back up an additional 4 or 5 GB, but then it stops again, and after that it only gets about 100 MB of additional data backed up before it just stops.
I have 80 GB of data on my internal drive, and hundreds of gigs free on the external drive, so space is not an issue. When I first encountered this problem, I did some research and found an article on this website by Apple to reformat the external drive. I did so, but it seems to have made no difference. I also later found some advice to, after a failed backup, drag the incomplete backup file from the TM disk to the trash and then start the backup over again, but that did not work either.
Does anyone know why this will not work for me? I can't even get passed the initial backup, and for me that is a little concerning.

Answer 1

UPDATE:
I have been playing around (frustratedly) and I do not think the problem lies in the external hard-drive, but in the internal one. The reason why TM won't back up seems to be because of the files on my computer. I look through the console to find out what files TM stumbled over, and I've begun excluding them as they come up. First it was the system folders, then it was my Aperture library, and now it's my iPhoto library. More specifically, there are data files for specific photos in my iPhoto library that seem to be corrupt. The console tells me that TM stumbled on them, and when I locate the corrupt files in the Finder to delete them, Finder crashes before I can do so.
I'm becoming very irritated with Time Machine and my computer. Please help me get this to "just work", I know it's probably something I did accidentally that's causing this but I don't know what or how to remedy it.