Internal Error in Quartus: GDFX?

Hello.

I am working with QuartusII. My project is Serial Mutrix Multiplier and I use Verilog, but when i compile my project the following error appears.Can you help me?

internal error: sub-system: gdfx, file: /quartus/synth/gdfx/gdfx_slice.cpp, line: 736

(*sgate_nodes) != null && (*sgate_oterm_coll) != null

quartus ii version 9.1 build 350 03/24/2010 sj web edition

service pack installed: 2