Time Machine Disk Self-ejects, and more

Question

I'm using a 1 TB FreeAgent GoFlex external USB drive as my Time Machine back up. Half the time it works perfectly, other times it suddenly ejects itself and I get a message about how the disk was ejected improperly. If I pop out the USB cable, then plug it back in, the disk remounts and goes on as before. Other times it will begin backing up, and seems to get stuck in "back up" mode. It keeps evaluating the main hard drive until it's time to shut down for the day. I can't make it stop. If I go ahead and shut down, the computer quits everything down to the bare desktop, then locks up. If I shut down while not stuck in "evaluating" the computer shuts down normally.
How do I make the disk quit self ejecting?
How do I keep it from getting stuck "evaluating" the disk?

Answer 1

I have a similar problem which only recently developed with my Seagate FreeAgent Desktop Classic. The drive ejects only during TM backups. Here's the message from the TM widget:
Starting standard backup
Backing up to: /Volumes/TM/Backups.backupdb
Event store UUIDs don't match for volume: Macintosh HD
No pre-backup thinning needed: 309.2 MB requested (including padding), 365.05 GB available
Unable to rebuild path cache for source item. Partial source path:
Error: (-39) SrcErr:YES Copying (null) to (null)
Copied 8845 files (84.6 GB) from volume Macintosh HD.
No pre-backup thinning needed: 534.6 MB requested (including padding), 280.31 GB available
Stopping backup.
Error: (-43) SrcErr:NO Copying /Users/angeloferraro/Library/Preferences/Macromedia/Flash Player/#SharedObjects/EC6L7AJD to (null)
Copied 8625 files (184.9 MB) from volume Macintosh HD.
Copy stage failed with error:11
Stopping backupd because the backup volume was ejected!
Error writing to backup log. NSFileHandleOperationException:* -[NSConcreteFileHandle writeData:]: Input/output error
Backup failed with error: 27
have reformatted the external drive which has not helped.
No problem if TM is switched off. No disk errors with Apple's native disk utility, however Seagate's drive manager reports that "the selected drive failed its most recent diagnostic test" but does not provide any further information.
Have sent an email to seagate and awaiting their reply. Drive still under warranty.