The mp3 player in Kurok and any Kurok derived engine does crash at the end of the song.
MDave avoided the problem by having the QuakeC restart the music one second before the mp3 music was over.
This meant he hardcoded the mp3 times per map name in the QuakeC and did a stuffcmd of "cd play <whatever>" when the time check indicated it was one second before the end.
Just extra information.
I'm not entirely satisfied with my MP3 music fix and some people like Downsider said it still crashed.
You can see my mp3 player "fix " by using WinMerge on "KurokQuake6" and "KurokQuake9" in the thread Xlink referred to and looking at the differences in psp\mp3.c -- which effectively just restarts the music at end of file. This is a workaround rather than a good fix in my opinion.