my macbook pro is spitting dvds back out when I put them in. Any ideas?

Also, I now have another problem. There is an admin password on the computer but since I use that account all the time I do not set it to require the password. Now it wants the password to move anything on the internal drive to the trash. Also, when I enter the password, the trash looks like it's been emptied but there is no more space on the drive so in fact the trash has not been emptied.

I have repaired permissions and have got as far as restarting with the command and R keys pushed and repairing from the disk utility there as well.

None of this solved the problems.