You may have a bad block on the drive which stalls the backup half way through. If you have Tech tool pro or an equivalent you may be able to check for this. If not and you have nothing on the disk use Disk Utility to reformat the disk but this time zero out all data. Use the Security Options Button. This will attempt to write out any bad blocks so that they are not used again.
How do you know it was 'stuck'? Leopard does many things in the background and it's been reported that some computers can take hours to set up Time Machine the first time. Also do you have enough space on the backup drive for Time Machine to work? And you didn't say what kind of Mac you had or what kind of backup drive you have, but if it's a PPC Mac then you need a Firewire drive for it to work correctly. The point is this could be anything, and not necessarily something with Time Machine
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Also browse through Apple Discussions on Time Machine:
http://discussions.apple.com/forum.jspa?forumID=1227
You might spot something there.
You may have a bad block on the drive which stalls the backup half way through. If you have Tech tool pro or an equivalent you may be able to check for this. If not and you have nothing on the disk use Disk Utility to reformat the disk but this time zero out all data. Use the Security Options Button. This will attempt to write out any bad blocks so that they are not used again.