If you have issues logging into any of the Forefront Management Consoles with an Error 500 you most likely changed the service account password.
To verify this is due to a password issue you can check the event logs for
Event ID 10004, Distributed COM
DCOM got error “1326” and was unable to logon <account name> in order to run the server:
{9738A91E-222B-4F3F-8962-6B01144D6ACB}
If that’s there you need to go into Com+ applications under component Services.
Get the properties of the MFSMC.Services object and change the password on the Identity page.
That should resolve the error.