Hy everybody.

I've got a TSSTcorp DVR+/-RW mounted on a NEC Versa P440 laptop with Ubuntu 6.10 or 7.04 (both act the same).

If I insert a disc in the unit (either CD/DVD) 20-30 minutes after entering the GUI (Gnome) the system will not mount the media automatically and freeze if I try to mount it manually. The only way to use the drive is to insert the disc immediately after startup or leave it in through the boot process. This way the media will be successfully be mounted and work flawlessly.

Another odd thing is that after a while of not using the media the disc is automatically ejected (no actions that I take can be blamed for the spontaneous eject)

I will take a guess, but that's all it is is a semi-educated guess..
As it is a laptop, I wonder could it be related to the ACPI system, either putting the CD drive into a sleep state or standby state, from which it is not resuming (or not resuming properly).
This mostly applies to your first half of the question, as to why you can't seem to access the drive after like 20 minutes or so.
As to the second half, (again Guessing) maybe the machine is planning on going into a reduced power state and is going to put the drive to sleep, so it wants you to take the disc out first.
You may want to look into the ACPI system and what it does/doesn't do on your machine.

Sounds promising. Can you give me some info on where to look?