Can't time capsule back-up to an external hard-drive? I recently had connected an external hard-drive to an old 1st gen time capsule and successfully used it for backup. However, my TC began shutting down on me so I thought it was time to get a new one. Now my new TC will let me choose my external drive but as a backup but cannot seem to login to it. It keeps complaining "problem with the network user name or password. However, I know this is right.

In the Mac Help doc, there is one section that reads:


  Every available disk that can be used to store backups is listed. If you’ve partitioned a disk, the partitions are listed. Time Machine can’t back up to an external disk connected to an AirPort Extreme, or to an iPod, iDisk, or disk formatted for Windows.


OK, so if this is true, why did it work before? Why does the app let me select the drive as "Available"? Could the reference in the Mac Help to AirPort Extreme refer to just the base station and not the time capsule?
I used Apple's Express Lane tech support. (Being as this was a brand new TimeCapsule, there was no fee.) 

The tech told me that TC no longer supports backup to an external drive as of the 2nd Gen TC. He would not speculate as to why.

I can speculate that perhaps Apple wanted you to buy a bigger TC instead? Or perhaps (as was my experience) backing up to an external drive seemed to cause the TC to shut down (maybe overheated).

However, I can and did hook the drive directly to my USB port and I can back up that computer to it using Time Machine software (which is what I wanted to do anyway.) 

Odd to answer my own question but this thread may provide an answer to the next guy.