Verify the 3D Mouse is enabled within your application. Some applications require specific steps to activate a 3D Mouse. Also, you may want to do a "repair" on your 3DxSoftware driver if it was installed before your applicaton.
I think it depends on the version of poser you are using. I beleive support for 3DX was only added in V7.02 so if you are running a version below that you need to install the 7.02 or upwards update.
I'm running Poser pro 7.03 and my SP is working fine