Some users (including me) have previously reported strange "500
internal server error". I finally found out that this is because of a
bug caused by debug_backtrace that was introduced in MW18. (seem only
to crash certain server configurations)
http://bugzilla.wikimedia.org/show_bug.cgi?id=8041
When I commented out all lines containing debug_backtrace, the 500
errors disappeared, but the page layout of Monobook started to behave
strangly. The navigation menu at the left was hidden by the main page
content.
I had to downgrade my site to <MW18 to make it work.
How can I avoid breaking MW18? Or do I have to wait for a future patch?
--
Harald