need solution momentum Substrate calculation failed

hello
is what you can indicate the solution of the following pb:
after the start any patch in momentum exuction

Simulation mode: MW
Design: feqs

Simulation started on: Tue Jul 05 7:14:58 2011

Substrate calculation failed

Momentum stopped ---------------- ----------------
thank you for your answer

Hi

We need to see what your setup looks like? Screen dumbs would help.