I just built a new system using an AMD 4200 X2 (dual core).  I reinstalled a bunch of my programs including Carrara 5Pro, Lightwave, Poser 6 and Vue.  I launched Carrara net render (using my old P4 2.5 and a Dell) and was blown away by how much faster my TWO new cores were rendering over the old P4s.  Lightwave also flew.  On the other hand, Poser 6 chugged along as before, perhaps somewhat faster render but didn't blow me away.  Bottom line, the program has to take advantage of the extra core and Carrara 5 Pro, Lightwave and I think Vue do (at least for rendering) and Poser 6 does not.   My take on the dual core is I am very pleased/impressed by its performance but would recommend them only after you've checked your programs to make sure they take advantage of them.

Thanks for your replies Ashley and Xantor.  It turns out that the problem seemed to be with my CPU/Video Card.  When I switched off the OpenGL render, the problem seemed to go away.  After trolling the internet for information, I discovered that there seems to be an issue with Nvidia's 80 series drivers and dual core/proc machines (I have an Athlon X2 dual core and a 7600 GT card).  One of the fixes involves downloading a driver from the AMD site.  Happily, after installing the CPU driver, I haven't had any problems with the pause key sticking and the overall perfomance of Poser 6 is much improved using the OpenGL renderer.

Got to agree, Carrara and Universe look good and are fast. Poser hurts the eyes.