I had mapped Ctrl + Alt + T to open a Terminal (using Settings -> Keyboard -> Shortcuts). I may have installed some new software yesterday, to be honest I don't quite remember, but today the hotkey is not working (and it has been working for some time). I changed it to Ctrl + Alt + 1 and it works fine but I'm used to T and I see no reason to change it.
I suspect that some other software is intercepting Ctrl + Alt + T for its own shortcuts but is there some way to figure out what would be doing that?