Which version of INCISIVE are you using (what does "irun -version" report)? (although I'd be a bit surprised if this is broken even in fairly old versions, unless it's really really old). I just took the code you pasted, and created two other files:
top.vams Code:module top;
wire in[7:0];
veri_dac I1(out,in,clk);
endmodule
and
top.scs Code://
tran tran stop=100n
Yes, I know this won't work because there's no stimulus, nor is there a ground node defined - I just wanted to see if it would compile and elaborate OK. I then ran:
irun veri_dac.vams top.vams top.scs
and it runs with no errors. Maybe the problem is elsewhere in your netlist? (not sure how though) - perhaps bits is defined to be something non-constant?
Regards,
Andrew.