I tried to contact Mark Carey with these questions but he's away and our need is urgent.
We run MT 4.14 with: Enterprise Pack 1.01, Professional Pack 1.1
The following plug ins are newly installed: Entry Post 2.92, MT Forum 1.06, Template Installer 1.2, IfAvailable 1.0
1. When I attempt to create a new topic, after I click on "Post" button, a window opens with the URL: /mt/plugins/EntryPost/mt-entrypost.cgi. It is blank. No topic is created. (The mt-entrypost script seems to be in the right location, and is a PERL script, but beyond that I can't troubleshoot).
2. The Topic template, and other templates also, give lots of missing tag errors, like:
at line 17 is unrecognized.
at line 19 is unrecognized.
at line 20 is unrecognized.
etc. etc.
Many thanks to anyone who responds.
-Peter
Reported on Movable Type 4.1x

Hi Peter,
What it working so far?
Have you made any changes which damaged it?
Are there any errors on the activity log or on the server errors log?
Why aren't you upgrading to MT Pro so that you won't have to rely on plugins for running a forum?
Kind Regards,
Mihai Bocsaru
what the differance with the PRO and this one ?
There are many differences, it is a much more evolved built.
However, porting your "theme" look and feel to the movable type forum template set would be a complex task and for that reason you may like to stay with the system you're currently on.
Actually, you may like to only upgrade movable type and your plugins, but continue to use the Forum plugin and Entry Post because of the differences in terms of html/css structure in between the native movable type forum template set and the one from Mark Carey's forum plugin.
You didn't reply to my questions...
Also, a direct URL to your project would help!
Thank you for your helpful advice, Mihai, and I'm sorry for taking so long to respond. We're currently trying to decide whether to use the MTForums plug-in, install the MT Pro pack or use a stand alone version of phpbb.
To answer some of your other questions, the error log shows PERL errors like [Mon Nov 30 13:29:17 2009] [error] [client 10.x.x.x] Subroutine category_class redefined at /var/www/movabletype/plugins/MTForum/lib/MTForum/Publisher.pm line 891.
The presenting problem is that when you try to create a topic through the forum interface you get an "Internal Server Error" page (with visible tags)
Thanks again for the help you've already provided.