the_permalink() returns no value

Hi folks,

I have a wordpress install that returns a null value from any the_permalink() call. It happens irrelevant of template – any page with a the_permalink() call returns null.

I assumed it was a mod_rewrite problem, but other rewritten urls output fine (eg links to archive months), and default permalinks also suffer the same problem.

Anyone have any ideas? Anyone come across this before? Any suggestions very appreciated.