I'm assuming that your iOS 5.x upgrade went fine? If so, try to 'force close' the Camera app, i.e. open the multi-task bar at the bottom of the iPad (double tap the 'home button' or use multi-fingering gesturing); find the Camera icon, press & hold until all start to jiggle - press the minus sign on the icon; return to the home screen and try again.
If not successful, 'Restart' and if not effective 'Reset' the iPad (directions HERE, if not familiar w/ the maneuvers) - please post back your results if further advice is needed!
Hope your camera is now working! Giradman had some great advice!
The IPad Forum is a community of members from all walks of life and from all over the world coming together to share our experiences and to help each other learn about this wonderful piece of technology the Ipad. There is a wealth of information already here in the many threads we have so doing some searches will answer most of the questions you have. If then you cannot find the answer you are seeking then by all means post your question. There are many friendly and informed members here only too willing to help you.