It worked!
Have you tried upgrading to a stable release of PHP?
PHP is
buggy at the best of times, but the release candidates are
often badly broken.
I know it's working for you with other applications, but that
doesn't mean it's MediaWiki's fault. There might be something
different about the way we call the session handling
functions, which is perfectly valid as documented but broken
in 5.1.0RC1.
Thanks Tim! You're right!!! My wiki finally works, and it was due to the
upgrading the PHP RC version the host was running. Now happily working away
with version 5.2.0.
Thanks very much for tip. It was exactly what I needed. Took nearly forever
to get the hosting co to do the upgrade, but they finally did this evening
sometime.
I really appreciate the help here folks.
All the best, Scott