When I try to burn CDs (Data or ISO images), it starts normally, and acts fine until it comes to the OPC part. After a few seconds, it gives an I/O error which is 'not necessarily serious', and then it says 'OPC failed, probably the burner does not like the media'. However, I have burned the same blank CDs on the same computer and the same CD drive before.
Is there a way to turn off OPC or would I not want to. Or is it due to some other setting that I am unaware about, like burning speed?
Or is the problem unsolvable and I need to get new CD-Rs?
I have tried using Gnomebaker too, but the same thing happens.

Using crappy media is handled by the CDR-W hardware. Flash the bios first, and if that doesn't take consider the idea that your CDR-W is dying or that you test with better proven media. You can ignore the error, but that doesn't eliminate the underlying problem.

How can I make k3b ignore it? Or should I use a different program?

You can use a different program like xcdroaster, but honestly I've seen this before and your CD writer is dying. It won't help if you waste your time and money on fubar'd CD's.

Oh.
It is a relatively old laptop and I don't think the CD drive is replaceable. I think I should just get a external/USB CD drive. While I'm at it, I might as well get a DVD burner too...