CZECHer - I don't see where you posted information regarding your setup. That would help others to help you. (Suggest updating your signature with the info for the future.)
What phone? Dream, G1 or MT3G? (32A or 32B?)
What radio do you have?
What SPL?
How is your SD card partitioned?
How did you wipe your phone before installing?
What kernel are you using?
Are you using a custom MTD setup?
How much room do you have left on system? (In terminal console, type "SU", press enter and allow super user, then type df -h.)
Camera not working isn't typical, so my guess is either 1) something is messy in your setup, leaving too little room in system or not enough RAM 2) improper/incomplete wipe before install, 3) Corrupt download or 4) your camera is broken.
If I had tried all the quick fixes and something is still now working, below is what I would do personally. This assumes that you are using a 32B G1 or MT3G and have a radio/SPL that is compatible with the CM6.1 stock kernel. This also assumes you are not using a Custom MTD partition layout.
1) Redownload the ROM and Gapps to rule out possibility of corruption. (leave on PC for now)
2) Download Ohsaka Super Wipe 2:
http://forum.xda-developers.com/showthread.php?t=834812 (leave on PC for now)
3) Remove SD card and using a card reader, backup all data to PC and reformat the card
4) Copy back data to card, along with new ROM, Gapps and Superwipe. Delete .AndroidSecure folder from card.
5) Boot into recovery and wipe with SuperWipe. Shut down and restart into recovery.
6) Flash ROM and Gapps, restart. (If you are using a 2708 radio/SPL combo or have a 32A, flash appropriate kernel.)
If camera is still not functional at this point, I'd be worried about a hardware problem.
Good luck!