A while back I found a 400mhz G4 Sawtooth for $5. After replacing the DVD-ROM drive with something I can actually use, it works except for one strange issue. Each time the G4 starts, it ejects the CD tray. It doesn't matter if there is a disk in it or not. So far I have tried an old DVD Combo drive, an almost new DVD+-RW drive and an older CD-ROM drive. It also doesn't matter if the Zip100 drive is attached or not.

The original drive cable is being used.

Any ideas as to why this is occurring?