mhond,
have you tried searching for the solution using the search function? your problem is a pretty common one. it was one of my very first problems with the N900. search and you will find the answer. kahit dun sa thread ni sir topet sa symb napag-usapan na rin yan.

plus, if you have successfully flashed your phone, you should be able to use your camera again. so it's either something was wrong with the way you flashed your unit or (wag naman sana) you have a hardware problem. sundan mo na lang yung instructions ni sir topet sa kabila for flashing para mas madali.