In order to manage 'Global' nets such as GND you should use special 'TAP' symbols with a NETNAME=GND property on them. This indicates to the system that the signals should all be connected to GND thoughout the design. There is plenty of information about managing global nets in DxDesigner here in Communities and on SupportNet.
See this discussion: http://communities.mentor.com/message/10641#10641
A useful source of info is App Note 10770 on SupportNet, it talks about Global Signal Name as a Property, this is for the Expedition flow, the equivalent Property is NETNAME in the PADS flow.
Thanks for the input, I will look into discussion that you recomended. Thank you for a quick response.
Rob is correct about naming nets for GND.
You need to check one more thing in PADS Layout, if you have to define one of the layers as CAM or Split/Mixed plane and associate a Net like GND with that layer. Doing Net assignment for plane layer will create thermal Indicators.
Thanks for the tip. That fixed my problem in PADS Layout, and I am off and rolling again.