[thelist] Premature end of script headers

I have an ad banner script on my site (WebAdverts) that is giving me a 
little problem. Hopefully, someone can tell me what is going on. I am using 
zones for this particular script and only 1 zone is giving me problems. For 
some odd and unknown reason, this zone script will not run and will 
generate a premature end of script headers error at random times. Strange 
thing is, the script runs fine the rest of the time.

There are no problems with any of the other zone scripts. My ISP is baffled.

Anyone have any ideas?
Chris