I put in an OEM CD player in my GFs 98 Civic EX. (It was out of either a 97 or 98 Civic – I got it from my friend's shop.) It worked fine for two weeks, but today, you put a CD in and it just says "CD Er" (or at least that's what my GF told me).

So, is there any troubleshooting advice you can give? It's obviously plugged in if it's getting juice. It just won't read any of her CDs.