I know that this reply is to a post a year ago, but it might help anyone with the same problem in the future. I also had this "Flash settings cannot be changed" message come up after using my H50 for several months with no problems. It was very irritating, because I missed out on getting some great pictures of my nephew on Halloween night because the camera was stuck in "no flash" mode and I was not able to change it. On this night I didn't realize I had forgotten my memory stick until I turned it on. Maybe this triggered the error, a bug in the software? Once the flash error happened, I could not change the flash setting in the Auto Adjust Mode, even after putting the memory stick back in.
After searching around the web, I found the solution to another Sony model, and it worked on my H50 as well. It is very simple, all you have to do is re-initialize the camera. I don't recall initializing the cameara in the first place. Maybe that was part of the problem? I originally set the time and date, but did not run the initialize process. I looked through the manual several times, and it never mentions the initialize process. It shows it as an option of the Main Settings, but does not say a word about it! love the camera, but the printed Instuction Manual is HORRIBLE! Maybe the PDF version is better.
Here is how it is done on the H50: Turn on the camera, press the HOME button, turn the dial until you get to MAIN SETTINGS mode (the little tool box picture), press the center button to get to the "Main Settings 1" menu. Arrow down to the "Initialize" option, press the center button to get to the initialize process, arrow up to highlight the "ok" and press the center button. Set the time and date, and your back in business.