My faulty burner! Should i get it replaced?

[nilo]

1 year ago i purchased a yamaha 6x burner which was fairly fast at the time. I went for the yamaha cause i thought it was a high quality brand. Anyway, a year l8r i'm having a bit of a prob with it. I can burn any cd's fine, but audio cd's that previously worked in my portable (battery operated) cd discman struggle to play and the last 5 or 6 tracks won't usually. They will work in the computer cdrom though. Seeing that cd's burnt previously still work in the discman i can only assume the burner isn't working as it should.
I wonder if it means the burner laser is wearing out and it's working but doesn't have the intensity it use to, well thats my guess.
I'm fairly positive its not the brand of CD's & i'd explain why but it would just waste space so just take my word.
Annnnnnyway the question is , whats is wrong with it and am i entitled to have it fixed or replaced (its barely within the warranty period ) Any advice greatly appreciated.
Thanks all
nilo