There may be someone monitoring these forums who can give you a tip on how to solve the problem, but they would need more information than you have provided.
Generally speaking, Filter Forge 4 works fine on Windows 8 in conjunction with Photoshop CS6, so the problem must be specific to your computer or workflow.
Please provide more information about your system and the steps to reproduce the Photoshop crash. Is Filter Forge 4 the first version of Filter Forge you have used?
Edit: Once again SpaceRay answered at the same time and was faster