ive had problems like this before and i just used different discs. and also what cd drive do you have and what discs are you using? there may be some incompatibility somewhere.
this sounds like my plextors when they started crapping out
i had 3 plextor 16x drives die on me, supposedly because of my less-than-adequate power supply
plextor was always my favorite brand, too
they'd stop reading blank media, sometimes i would have to eject and reload 2 or 3 times before they'd read, and eventually they stopped reading discs altogether
firmware flashes would sometimes fix them for a day or so, but then they'd start acting fussy again