http://www.movabletype.org/support/index.p...90&hl=500+error
http://www.movabletype.org/support/index.p...03&hl=500+error
I have resolved the issue with the help of my hosting.
Apparently the cause for the problem is the fact that they have enabled mod_security
From my hosting provider.
QUOTE
The previous error is due to we have enable mod_security with apache (URL scan) and this has prevented the url containing certain symbols from performing the safe function properly.
Hopes that help anybody else that is having the same problem.