avast! Detected unauthorized modification ...

Hello folks,

I have a problem in ADNM when I run this. Before the program load I get a message like this:
avast! detected unathorized modification of this program (c:\program files\alwil software\management tools\asaAdnm.exe)
Continue can be dangerous. Run the program anyway ?

How I can solve this, Is this a ADNM problem or OS problem ?

Thanx!