As Mike will probably remember we have had an email exchange regarding the advertiser signup page on a Windows server not being displayed, although there was no obvious PHP error that should cause it.
After a month of other activity I came across the same error elsewhere and got to dig in to the error again.
Then I came across
this article which solved the problem once and for all.
For those who do not like to click through:
The error is caused by the code using the <? tag instead of the <?php which is accepted on most linux installations but not always on a custom PHP as most Windows servers are.
Solution (other than letting the developers clean up the inconsistent code) is to use
short_open_tag = Onin the php.ini file.
I am off to try getting advertisers, hopefully this will help others at some time.