I just purchased this camera and inserted a memory card. Now, when I try to take a picture, I get the 'card protected' error. How do I remove this error and take pictures?

Without knowing the make and model of this new camera I can only speculate on the problem however in my opinion you need to unlock the protected card I'm giving a diagram of an SD card here.

Slide this little switch to the top or towards the gold contacts.
Another thing you will need to do is format the memory card your camera may call this initialize.
Formatting a memory card makes it ready to accept information files from the camera. I hope you have your manual because without knowing the camera make and model i can only suggest where to look for this feature. Most often this function is in the set up menu, once the card is unlocked you need to find this format highlight it and press the okay button once done the camera will function properly as long as you have set the day date and time. Day date and time once set is held in the camera internal memory so you don't have to input the information each time you turn the camera off and back on again. Happy New Year