The CD-R tray keeps opening on my mini-tower for no apparent reason.

I am currently running Ubuntu 12.04 LTS after having tried 11.10 for about 6 weeks. The tray opened on 11.10 as well. My system also has a DVD drive which does not open.

My system is an older (5-6 years) min-tower which used to run Win-XP. It has an Intel Celeron 2.4GHz CPU with 1GB RAM. Apart from being a Genuine Intel motherboard, I don't know the exact model.

The CD-Writer is a Maxtor 34098H4 MAXTOR 6L080J4 - tray opens.

The DVD drive is a CR-4804TE HITACHI DVD-ROM GD-7500 - normal behavior.

The CD tray opens whether I'm using the computer or not. My work-around is to leave a CD-ROM in the drive - with a disk in the tray, it does not seem to open. In all other respects, both optical drives work properly.

Has anyone else seen this? Any suggestions for a fix? I am new to Ubuntu so I will need step by step instructions