Don't know what software you're using to burn cd's, but the stock cd player won't play mp3 files. Some software will convert the mp3's in your computer to wav files seamlessly, you may not know it's being done as your disc is being made. Some software may just burn the mp3's onto a CDR or whatever, and if that's the case, the stock cd player won't have it. It needs to be converted to a wav file.
But if it's 'skipping' then it WAS coverted to a wav file, a mp3 file won't play at all, it'll just read 'error' and eject the disk.
Blank cd-r's are not nearly as hardy as store bought cd's. they are really sensitive to UV light, heat, and scratches. I keep mine in these little sleeves i got at compusa for like a nickel each. It seems to help.
The quality of the blank media is also an issue - there's really only a handful of companys that make media, regardless of the name on the box. The best is probably Taiyo Yuden.
If you label the disks with a sharpie pen, that stuff can soak down into the disk and mess stuff up. Write really small, and on the outside edge of the disk, and don't use all 80 minutes so the sharpie ink isn't on top of data -- helps with mine.
I'm also finding the cdr's with the blank white printable label hold up better than the regular, plain labels.
Hope this helps. But there' still a pain - someday I'll install the aux mod and get a Zen 30 Gig'er myself. I'm so lazy, I'm barely writing this.