Try checking the settings for your camera, remember what you have done lately on your phone and bring it back to its previous state. play with your camera settings, try a little bit of experimenting on your camera settings and match it with restarting the phone. if this doesn' help you, you may try updating the phone camera firmware itself.  i would not guarantee that this will work but at least give it a try.   1.  from your keypad menu type this code *#6984125*# it will give you the admin setting 2.  select internals 3.  press the message box and type the code *#9072641*# press done, press confirm 4.  select test mode 5.  select video by pressing 6 in the message box and press ok. 6.  press 3 ; camera firmware update 7.  wait till it says success or complete 8.  press back , press end key (call end key) 9.  then restart your phone.
hence, you can do a hard reset or factory reset if you feel you don't want to do the steps above. to do a hard reset or factory reset do the following steps. 1.  back up your files, ex.. contacts, task, notes, photos images stored on your phone memory 2.  disable any locks or security locks, ie, privacy locks, sim locks, network locks.  3.  switch it off, remove battery, sim and memory card 4.  reinsert battery, make sure it is fully charge.. 5.  switch it on 6.  from your keypad type the code *2767*3855# 7.  the phone will do a hard reset and will reset to its factory setting. 
be aware that it will remove all user settings from your phone. 
good luck and regards.