Open case form by url

Hi

I want to open case form using parameters I supply for this.

It works when I use a url like this:

http://....main.aspx?etn=incident&pagetype=entityrecord&extraqs=primarycontactid%3D%7B43b58571-eefa-e311-80c1-00155d2a68c4%7D%26primarycontactidname%3DYvonne%20McKay%20(sample)#796270740

It sets Contact field but when I want to set Customer Field it does not work and hangs on:

http://.......main.aspx?etn=incident&pagetype=entityrecord&extraqs=customerid%3D%7B43b58571-eefa-e311-80c1-00155d2a68c4%7D%26customeridname%3DYvonne%20McKay%20(sample)#