mplist procedure reports error but mpcert and mplist1 seems ok

Many people run through a problem with a MP on a primary site after upgrade from SMS 2003 SP2. The mpcontrol manager states that the MP is not responding to HTTP requests. "Internal Server Error 500".

When testing MP service with the following:
http://servername/sms_mp/.sms_aut?MPCERT Works
http://servername/sms_mp/.sms_aut?MPLIST Fails with "Internal Server Error 500"
http://servername/sms_mp/.sms_aut?MPLIST1 Works

There are a several queries you can execute against the SMS database to confirm this issue:
exec mp_getmplistforsite 'sitecode'
Select * from sites
exec mp_getlistofmpsinsite 'sitecode','0'

Open SQL Management Studio, go to:
*servername*\Databases\*sms/sccm database*\Programmability\Stored Procedures\dbo.MP_GetListOfMPsInSite
Click "new query" and run the following query:
exec MP_GetListOfMPsInSite "Central Site code","0"
This should return you a list of all MP's.
Now check the 4th column where it says "Capabilities" all MP's should have the following value there:


If there are sites that have no (blank) value or a NULL value, these are the cause of your HTTP 500 error, all MPcontrol.log files on all your secondary sites and your central site will return that HTTP 500 error.

A full reinstall of a site could resolve this issue.