Texture filtering usually causes these seams in the render. Turning off Texture Filtering in the Poser Render Settings will usually resolve this.
To do this in Poser 6, go to RENDER --> Render Settings. Change to Manual Settings and uncheck 'Texture Filtering.'
In Poser 7, this must be done 'per texture.' You will need to select each texture and then turn off the texture filter setting for it in the MATERIAL ROOM. Please see the Poser 7 user guide for information on how to locate this box.