What is Wrong with Time Machine?

So for those of you who use Mac OSX Leopard, you know how great and useful Time Machine can be. For those who don't know what Time Machine is, it is a built in backup system for OSX which synchronizes your data at specific intervals to an external drive. It's great for someone like me who does a lot of writing, and e-mails and doesn't want it all to go away with one bad save or trashing of a document. When I first upgraded to Leopard I had no issues running Time Machine, I bought an

Iomega 500GB External Drive

from Apple, and felt as though I was not going to have to worry about my backup any longer. Well I re-installed OSX a few months back because I was feeling the clutter of a year old notebook, and I had my data backed up and when I re-installed OSX I recovered all of my data and began to use Time Machine like nothing had happened.

Time Machine OSX

One day out of no where I got an error message saying that Time Machine failed to complete my backup, I thought it might be a fluke so I tried it a few more times with the same results. I read online that people were having similar issues so I followed their advice and reformatted the hard drive. Two months later and 30 different methods later I am still not able to use Time Machine. If anyone has any idea why I can get only 50% or so of my backup done followed by an error message that would be great. All I know is that its frustrating as heck. I am trying to be good, I want to backup, I have been foolish in the past, and even when I want to be good Time Machine won't let me!

UPDATE:

As soon as I posted this my next stop was at Digg.com, and low and behold there is a Mac 10.5.3 update that was released today that was suppose to help reliability on Time Machine! When I get home today I will test out the new update (which I have already installed) and see if that helps my Time Machine predicament.

UPDATE #2

: After installing 10.5.3 which was to fix some areas of Time Machine I am still having the same issue, it is still telling me that it unable to complete my backup. Back to the drawing board.