I want to submit this surely rare bug, due to an incorrect user operation. In this sense in not exactly a bug. The problem occurred with the Designer. I have loaded a layout, say A, in memory, then, thinking not to need it anymore, before loading another one, I have erased it (A) (with right mouse key inside the OpenFileDialog that I was using to open the new layout). After that, the IDE gave an error and the only way I found to exit has been to close it with the Windows Task Manager. Luckily I previously saved the code in memory and this had no bad consequences, but if it was not so, perharps the code in memory was lost.