The new version of icecast does an optimization to merge metadata with preceding mp3 data and sends it as one chunk, to reduce the number of send() calls.
If this send succeeds only partial ...
We believe we have found a bug in Icecast in version 2.3.2 (not the the released code but a version that was taken from a tag around the 2009.03.24 and it looks that it also affects the last version ...