I've found that only certain files can be sent, .zip, .mp3, .jpg, etc. If I try to send .ini, .exe, etc. those files fail. If you find that a file fails, try zipping it up and sending the zipped file.
How I fixed this on a rooted Droid X (should work for most Android phones)
Again, must be rooted
Rename /data/system/accounts.db to /data/system/accounts.db.bak
Soft Reset phone
Go to Settings -> Accounts
Backup Assistant took a few seconds to appear on my phone
Click on Add Account
Add the...