Well. This is the first time I ever had any trouble with my 4.5 years old Canon 7D DSLR.
I was on my cruise trip to Puerto Rico. I don't have backup camera with me. My 7D went into error 30 shutter lock mode after shooting few 3 bracketed HDR photos.
After searching on Google, I see many people have the same problem. The error 30 basically means the shutter got stuck in the open position. Or it's getting sticky due to the environment.
Now I've found two solutions in summary.
Remove batter and compact flash card off the camera. Wait for few seconds before putting the battery and card back into the camera body.