i don't have any boris effects, but zaxwerks effects will usually crash if multiprocessing is enabled, so you might try disabling mp and see if that helps (preferences>multiprocessing).
another possibility is opengl. if the effects have an option to use opengl, gpu or hardware acceleration or anything like that, try disabling that option. you can disable opengl in the previews preference, but the effect may also have an option, and you'll want to make sure that is off too.
note: if you have the caps lock key on and apply an effect, it won't start rendering the preview, so it shouldn't crash until the caps lock is release. this can allow you to apply an effect and look for a gpu option.
I have just managed a short test today after carrying out all your suggestions and it seems to have cured the problem. Sadly I didn't try them separately so am unable to tell which, or, if one was the cause.
Thanks again for you help.
Hi Jon thanks for your reply,I will give it a try. It's strange that I have not had a response form Boris. The only progs installed on the comp are CS5 suite and Boris. I was hoping that using a better Graphics card that Boris would have worked smoothly.
Thanks for your help will post an update.