Congratulations! I think you've found a bug. I don't use WMV files, but I'm puzzled this hasn't been reported by anyone else. My tests seem to indicate the problem is the last entry in the file extensions list is being ignored. When I add a dummy ZZZ extension, then WMV files are recognized.
I downloaded the program and I found it perfect!!! Except from this annoying thing: In the folder I have my video files, when I choose the "scan folders for new movies etc" it finds and lists all the movies except from the wmv files! And yes, I have checked the precerences and says .wmv among the other files (.avi, .mov etc) Is this a bug of I am doing something wrong? The funny thinf is that I can import the wmv files one by one from the new movie master.