If you read the error messages he posted, you'll see that Swatter reports agUF's version as "v2008-08-06". Looking at the agUF project page's list of files, there was indeed a version released on that date (r79879). There have also been 25 newer versions released since that date.
r79879 was released months before WotLK. Your error is almost certainly caused by you using an addon that is NOT compatible with WoW 3.0. Update to any version that is remotely recent, and your errors will likely disappear.
In the future, always make sure you have the latest version of any addon before posting an error report. It is a waste of everyone's time (including yours) to post error reports about outdated versions of addons, because in the overwhelming majority of cases, the errors you're reporting were already fixed. It's annoying for other people to have to play detective to figure out what's going on, and annoying for you to have to wait hours or days on a response that just tells you to do something you could have done yourself to totally fix the problem in about 30 seconds.
Curse sucks imo it has annoying popups and wants to run in the background.
Also is there any disadvantage in wowmatrix other then it uses others sites bandwidth and other reasons why authors dont like it.
Like the addons that it updates are its updates older then the newest version ?.
I'm still having these problems btw to the degree that the party frames crash when adding/removing party members
hmm it's weird because it's now up-to-date with curse.
However i dont know what could be causing these errors. i think it might be some addon clashing but i dont know what one it could be.
Edit: I just downloaded the curse client but it only picks up 22 of my 128 addons
Why don't you disable Carbonite to find out? I haven't seen any other threads with people complaining about errors with agUF. If agUF works fine by itself, then it's another addon. And are you certain you're running the latest version?