There are a number of other possible causes...

Many people were reporting this a while ago due to some sort of disk problem - the area camera was trying to write to had become write protected, causing the app to fall over. I'm sure a bit of searching will find threads on the topic.

i've also had it due to a physical problem - having sent the device back to Nokia they reported back there was water damage on the camera chip. Given I experienced the problem the first time I tried to use the camera after getting the device as a replacement for one with a detatched USB port, I argued it was thier issue not mine and eventually got yet another replacement.