Actually, it's not needed a complete re-flash. I found out it's enough re-installing maemo software from Nokia OVI Suite, but in any case you have to re-install the whole set of your apps. Fortunately, the configuration of some of them still remain in the phone after SO reinstall.

In my opinion it's not a matter (only) of apps using camera or related to. I've removed flashlight, mbarcode, frontview, blessn900, fcamera, lowlight, hdr... and rebooted again and again. Nothing!. It also happens that if you try to use flashlight, application doesn't start because "camera is being used by another app". In any case, I'm suffering other kind of problems: cannot go back to stock kernel (uninstalling power-kernel), calls don't finish automatically after the other one hangs, errors in dpkg when installing and uninistalling apps (this might be due to another issue with catblock app), etc. and really don't know if they are all related.
I have no idea but i guess it might be related to last CSSU update (camera-ui), pr-fremantle, power-kernel and some of these camera apps. Maybe the order of installation.