Time Machine not working correctly

I have been using Time Machine on my 2006 iMac (Leopard 10.5.8), for about 8 months with no problems whatsoever. All of a sudden a few days ago, this popped up: "Unable to complete backup. An error occurred while copying files to the backup volume."

I checked and found out it hadn't done a backup since Dec. 24. Tried backing up again, and it will run abut 5 minutes, then the error will pop up again. I have formatted my External Drive, and same thing happens. I have a 300 GB Iomega external drive, with about 64 GB of info to backup from my internal drive. It backs up about 979 MB before it quits. I have also run all the repair Disk functions on the Iomega, and all seems well.

I also downloaded SuperDuper (which I used to use before I upgraded to Leopard, and started using Time Machine), and it also would not complete a backup. Any ideas??

Thanks,
Steve

How old is the external drive?
Around 4yrs I replace them especially if used for TM.

2 1/2 yrs

What does Disk Utility say about the external drive when you run repair Disk selecting it in the left hand pane? If not an external sadly history.

It checks everything and says....the Iomega hard Drive appears to be fine. I can store items on the drive. I can delete. I have formatted 3 or 4 times, after unfinished backups.

I ran a SuperDuper backup again, and it also stops at about the same point as the Time Machine backup, so this obviously seems like a hard drive issue, but the repair disk says it's ok. I don't know. The hard drive is still under a 3 yr warranty...guess I'll check into getting it replaced.

Steve

CORRECTION: The SuperDuper backup actually copies 60.1 GB of info before it fails...Also, I am running into the rolling beach ball quite a bit. The computer might run fine for 20 minutes, then I will get the beach ball. Sometimes only for a few seconds....sometimes to the point where I have to reboot.