Just to help maybe someone having the same problem, i found this:
CSCeg89017
Symptoms: MGCP calls fail with a fast busy signal. When you enter the debug mgcp packet command, the output indicates that the 400 Voice Call Setup failed.
Conditions: This symptom is observed when MGCP PRI backhaul is configured on a Cisco 2800 series that is configured with PVDM2 DSPs. Calls fail only after the router is reloaded. The symptom may also occur on a Cisco 3800 series that functions in the same configuration.
Workaround: Enter the following sequence of commands:
1. Enter the ccm-manager config server ip-address command followed by the ccm-manager config command.
2. Enter the shutdown command on the voice port or on the T1 controller.
3. Enter the no mgcp command followed by the mgcp command.
4. Enter the no ccm-manager config command followed by the ccm-manager config command, assuming that you have the TFTP server defined.
5. After you reload the router, enter the write erase command, add the configuration, and save the configuration.
The Bug seems to be related to Cisco IOS Gateway version 12.3(x).
See Link:
http://www.cisco.com.ru/univercd/cc/td/doc/product/software/ios123/123relnt/xprn123t/123tcavs.htm
