You should check if the car stereo can cope with V2 tags. Perhaps it only likes V1 tags and therefore hickups when it reads the data of the V2 tags - which are stored at the beginning of a file, while V1 tags are stored at the end.
Also, the character encoding could be a problem - see this thread about encoding:
/t/2785/1
Sorry, you have to try it locally, but these the knobs to twiddle.