I've always thought that CD/DVD Writers are more reliable generally with many different media because they have better (or more sensitive or something) laser assemblies in them due to the fact that they have to read and write so many different formats of disks.
I don't think I've ever read or heard that, it's something which seems to be right after using optical drives for so many years. I've always found that tricky or difficult to read media are more likely to be able to be read in a writer rather than a plain ROM drive.
Also, I guess it would be fair to say that as almost all optical drives sold these days ARE writers, that if you have a ROM only drive, chances are it's getting a bit long in the tooth, and that's another thing which I have found to contribute to inability to read finicky media, ie. a "tired" or worn out laser...it may also be that your motherboard based IDE controller is crapping out - more likely cables and drive failure though...
If the drive used to work well...consider the cable change as Mike suggested, or it may be that the drive is just getting tired, they don't build 'em like they used to you know...Why build a drive which could last for 8 years when they want you to buy a new drive every 2 years?
I don't know what the Dell person you spoke to was on about, sounds like he was talkin out his butt-trumpet to me...
If there is a visible "ring" around the drive, often that is the demarcation between audio content, and multi-media content (ie. maybe the disc has a video clip on it or something)...