You don't need to turn off your computer! Damn son! Do you want your computer to break? If it whitescreens, go CTRLiALT-DEL, right click tekkit, or technic or whatever program is associated with technic, click goto process and end process. This immediatly stops it so you don't have to give your computer a hard shutdown. Also, clear your cache, and make sure your not using a dev version.