Time Machine backup to AEBS with ext HDD not working for one system

Mods, if I have posted in the wrong forum please feel free to move.

I searched all over and could not find anyone else experiencing this. So here goes-

Got a great deal on a 2TB WD USB HDD last week so that I could take advantage of Time Machine connected to our Airport Extreme Base Station. We have four computers total that will use this backup (2009 13" MacBook Pro, 2007 MacBook 2.0, and two Dell Mini 9s running Snow Leopard).

More specs- Airport Extreme 802.11n (2nd Generation) running firmware 7.5.2 (latest).

First mistake I made was going around with the USB HDD and backing up via Time Machine to each one. I then found out that if you want network backups you have to start there. So I reformatted and started over. First I did the two Mini 9s since they didn't have much data on them. Then I went to try my MacBook Pro and received the following error-

​

I went on and continued my backups with the other three systems, all of which work fine. But for whatever reason my MacBook Pro refuses to work. I can confirm access to the drive because I can read and write to it from the network. It seems that only Time Machine on this system has the issue. I did just notice that my MacBook Pro is the only machine updated to 10.6.8 so far. Perhaps that has something to do with it?

Has anyone come across this issue before? Do you know how to fix it? I understand that this process is not exactly support by Apple but I just find it strange that it works on three machines but not this one. I'll update the MacBook to 10.6.8 and see what happens but if anyone has any ideas in the meantime I would appreciate it.

 

I wanted to bump this and add that I just performed a reinstall of my operating system. Before I migrated my data from my other backup, Time Machine would work fine with my USB HDD attached to the AESB. Once I migrated all data though, the issue returned. Any help on this would be much appreciated. Is there a plist file or something I can remove and regenerate for Time Machine?