Designing PCells in Virtuoso

Hello,

I'm using IC5.0 Virtuoso to build PCells for MOS transistors. I would 
like to draw several fingers using the "Repeat in X" functionality. I am 
able to use the same the same functionality to put several contacts to 
the gate according to the gate length.

When I try to add any other shape to the group to get several fingers 
(e.g. the poly gate shape), I get the following error when compiling the 
PCell:

*Error* fprintf: argument #1 should be an I/O port (type template = 
"ptg") - nil

Can anybody tell me what's wrong? TIA

Paul