car: 95 gsr

has anyone here experienced or know about a clunking sound everytime they shift gear? this just started happening to me tonight and i don't know if it's safe for me to drive it to work tomorrow. it's a weird yet extremely noticeable clunking sound coming from underneath the gearbox everytime i shift gear. sounds as though something is loose. my car runs normal when i'm just cruising w/out shifting gears but once shifting starts again, i hear that sound and feel like my car is unstable. any comments or advice greatly appreciated!!!!!