Q: mouse and keyboard freezes since update to 10.7.5

After updating to 10.7.5 the mouse and keyboard freeze at least once a day. i can move the pointer but the keyboard and click functions don't respond. after restarting i get the message "The disc you inserted was not readable by this computer". how do i solve this one?  ( i've also had one kernal panic since the update which i have never experineced on this imac before) -  i also installed an extra 8gbs of kingston ram whitout any problems a few days before updating the system in case this is relevent.