Sure, there's a way to save it. According to the Apple web site, iTunes stores your backups here:
Mac: ~/Library/Application Support/MobileSync/Backup/
Windows XP: \Documents and Settings\(username)\Application Data\Apple Computer\MobileSync\Backup\
Windows Vista: \Users\(username)\AppData\Roaming\Apple Computer\MobileSync\Backup\
Just navigate there, copy it and then put it somewhere else on your computer.
A word of caution, however. If you save the backup, and then delete the backup and then are able to successfully create a backup - it IS the old backup that was corrupted. So, saving it will be of no use, because it's no good (iTunes couldn't read/use it).
So, if this works, may I suggest you delete the backup you saved "just in case" - else you'll just be keeping "junk" on your computer...
Marilyn