Dreamcast starts to crash more and more often !!!

[GuitarmanESP]

Hey guys,

I've got a big problem,
since I bought some game copies on cd-r via ebay and use them,
my Dreamcast starts to crash (and restart) more and more often !!!

Everytime I try to play a game (even the original ones), the Dreamcast simply reboots after some time. Again and again, so playing gets impossible !!!

The guy who sold me the copies told me, I have to be patient, because the laser of the Dreamcast has to change itself to play that cd-r -copes correctly ... but that wasn't right, it gets worse everytime I try to use my Dreamcast ...

What do I have to do to fix that problem ?

Thanx for your help !!!