Mine is the same. I was a great fan of nokia's but I would go with a different brand now. Tried restoring factory settings, the things a pain in the **bleep**. Shame because I loved the phone.
I know this post hasn't been updated for a while but I had exactly the same problem on the 6700 with 'Camera stuck on standby'. To resolve I found that the Gallery -> Images folder had large files in there. I cleared about 20mb of space from the folder and hey prosto, Camera is now fully functional.
May not be the solution to all the causes to the problem, but worked for me. Hope this is of use to someone