I had an error message. Unfortunately, I didn't pay much attention to it, so I could not tell what the message was. But since then, I cannot change most of the buttons' properties anymore.
I noticed that suddenly the font size was too big, although the size of the buttons has not changed. Before in size 25, all letters could be seen properly. After that message, I had to reduce the font size to 17 to make all letters properly visible. I also cannot change the shape of the buttons anymore. They stay rectangular, no matter which shape I choose.
I already closed the app and reopened it—still the same.
Actually there may be some form of corruption in one of the background files that define the Project file (.aia). So I think you need to upload you Project file here for a Power User to examine. Have you been saving Backups? If so, and the most recent Backup seems to be OK, upload that file too - it will help us to find the fault.