I think something happened in the code that caused csound to stop
finding looping info stored in WAV format headers.
I generated my own wav sample with looping info using libsndfile, and
it worked on 2012-04-07 with the debian unstable packaged of the time,
which was built from 5.15.
There have been two debian packages since then, both of 5.17, and I'm
not sure which one broke this.
I'd be happy to do more testing, but I'm not sure what info to
provide. Right now, I'm kind of hoping someone will have an "a-ha"
moment based on this report and know how to fix it.