I'm not real familiar with Poser, but in most programs increasing the light quality will help with this. Looking at the settings visible in your screenshot, if bumping up the Indirect Light Quality does not help, try increasing the Pixel Samples. Increase the samples slowly though - that setting will probably increase render times significantly.

Also, just as an aside (again, I'm not real familiar with Poser so this could be totally wrong), you might want to un-check the SSS box - any subsurface scattering on that one character won't be visible at that size/distance and it is probably slowing your render down to calculate it.

You might get better answers asking this in the Poser specific forum - you posted this (maybe accidentally) to the Community Center forum. :)