hmmm....let check this step by step....

1. you buy or burn the cdr yourself? if those bought from pasar malam should have no problem. if burn yourself then you need to check to see if you have burn it properly ad data cd.

2. is the the most basic. is the songs in the cdr "xxxxx.mp3" or something else? is it "xxxxxxx.wma" or "xxxxxx.ogg" or "xxxxxxx.m4a" which usually doesn't work with a lot of player. to make sure all songs can be played, then all files should be .mp3

3. if all is ok, then check to see if the cdr is detected by your HU. see if there is any error on the display. if the HU give error that the cdr cannot be read or detected, means the cdr is not compatible with your HU. if the isplay give message that can read the cdr but cannot read the file, then meaning your MP3 files are too high bit rate where the your mp3 player cannot decode.

hope this helps.