ihacker,
First of all, Welcome to the Apple Discussion Forums!
As the previous poster asks, you will need to post back with further info.
*Is the software that you are trying to load an OS upgrade or third party software? Is the software compatible with the OS installed and the system hardware of the computer?
*If you are sure that there is no disk stuck in the drive, what happens when you try inserting the cd in question? Will it not go into the drive or is it just spit back out immediately? Have you tried inserting another cd in the drive to make sure the disk is not defective?
Without further info, we can only guess at what the problem might be.
Post back,
littleshoulders [:-)