I have the same problem with mine. I talked to the geeks at a couple of local game stores, they told me that the first generation PS2s have this problem of not reading CDs, DVDs, and some games. So if you have a early model PS2, I had mine resereved before they came out, you will probably have this problem if you havn't already.
Mine is sitting on a shelf, and has been for about 4 months.