User interface freezing

After running for a few hours and changing between different gcodes the user interface will freeze. I am still able to control it through the web browser. The mouse curser is able to be moved around but nothing will respond on the screen.I have tried changing to a new micro SD card, reflashing the system and changing back to the stock screen. I am using the current version of software 1.2.1. This started after I downloaded and the 1.1.1 version and reverted back to the 1.0.9.