Simulating "streamed-in" gds files

Hello All,

I have "streamed-in" a gds file, and would like to simulate the design. I extract the parasitics, and in the extracted file, I "attach labels" and "created pins from labels". When I try to create a netlist, I get an error that effectively tells me that it the design was changed since the time it was extracted". Therefore, I tried "attaching labels" and then "creating pins from labels" before parasitic extraction. But, this time, the parasitic extraction fails, after telling me that there are too many pWell and pBulk layers on the labels.

 Can someone please let me know how to simulate the streamed-in designs from a gds file? 

 Would really appreciate some clues.

Thanks and Regards

Sirrius