Hardware :: IBook G3 Combo Drive Keeps Rejecting Disks

I have a " 12Mac iBook G3 (700mhz/128mb/20gb) with combo drive (12.1 16VRAM) Toshiba DVD-ROM SD-R2102. System software installed: OS 10.4.1. I'm a longtime Mac user (have a beige G3 desktop at home and a blue and white G4 desktop at work fairly familiar with OS-X), but by no means a true technie. My brother borrowed it for a couple of months, installed some software he needed to do some work with, then shipped it back to me via UPS. Now, the CD/DVD drive rejects all audio, data or video disks -- the drive whirs for anywhere from about 15 seconds to a couple of minutes, then the tray pops back out. Some disks seem to stay in the drive, but no icon ever appears on my desktop and no interactivity begins with the disk. I've tried inserting disks 30 or 40 times and maybe 3 or 4 have mounted to the point the disk icons appeared onscreen. Of those, a couple were audio and did not start to play music (although in one case, I got iTunes open and the tracks seemed to be registering).

In another case, I got a software CD to mount and tried copying its contents to my desktop , but an hour and a half after it started trying to copy the files, an error message appeared -- sorry, didn't manage to write it down). I have tried booting it up with an old OS 9 installer CD and that seemed to work (although the splash page was the gray apple with spinning gear beneath it -- not what I expected to see from a system 9 cd startup?). A friend told me to try that and if it worked, it might indicate this is a software-related problem rather than hardware, but I don't know. Prior to rejecting disks, the drive seems to whir at a fairly normal volume -- nothing violent or unusual. Sometimes it sounds as if it is working hard and sometimes it is fairly smooth sounding, but as I said, I haven't been able to really DO anything with a disk of any kind since receiving it back from my brother. He says it worked great for him -- before and after he installed some new software -- and that he was using audio, visual and data disks on a regular basis while in his hands.

The computer and all programs seem to work just fine -- except for the combo drive. The only other thing I can add is that he managed to lose two of the remaining rubber feet off the bottom, so now only the battery corner has a rubber foot. Does that slight imbalance make any difference to the reading ability of the drive, by any chance? Any suggestions you can give me to check the cause or cure this problem would be greatly appreciated. My brother is in the dog house with me, yet I do believe him when he says it worked great for him. Also, the shipping container looked fine and he did a good job of bubble-wrapping it. IF it had been dropped by Mr. UPS, could this have caused a problem even if the box looked good? (Shipping was insured, by the way.)