Doctor, I’m sick - fix me — but I’m not going to tell you what’s hurting 
Seriously — you need to provide some useful information that can be used to try and diagnose the problem.
What version of GP4? What version of the OS? Is this a new problem or has this always happened? What changed on your computer? New plugins? Updated plugins? Updates to your OS? New applications added? New/changed audio interface or new/changed drivers for it? Changes to your gig file? Does it happen with every gig file or just one of them? Is this happening during loading or while your performing? Does it happen with a particular rackspace or song?
Etc., etc.