Since some time, the Simple User Interface (i.e. the one started by for example clicking the "avast! Antivirus" icon on the desktop) hangs shortly after starting it.
It gives the "splash" popup, i.e. where it says "Testing of Memory and Startup", etc. When the splash popup has finished, avast hangs. There is a "avast! Simple User In.." 'bar' on the TaskBar, but (double-)clicking that does nothing. Right-clicking it only gives the "Move", "Close" and "About avast!..." choices. "About avast!..." works. "Move" does not work. "Close" works", i.e. closes the process and its bar.
This means that I can not use avast to scan any files.
Any suggestions as what could cause this or/and a recommended fix?
Note that the Standard Shield and Internet Mail work normally, i.e. e-mail viruses *are* caught, etc.. It is 'just' the Simple User Interface, and hence a manual scan, which does not work.
Thanks in advance for any and all responses.