Debugging Analog Errors while simulating VHDLAMS behavioral

Hi

Could you please help me out in debugging the analog Errors while
simulating a VHDLAMS transistor level designs.

The error from spectre looks like:

"Error found by spectre during DC solution estimation, during IC
analysis,
during transient analysis `amsAnalysis'.
Matrix is singular (detected at `tb_output' and `uInv.A1.irn').
ncsim:*E, RNALER: simulation terminated due to analog error"

I have no clue how to debug the Problem
Thanks in advance. your help is awaited.

--Srinivas