It is just that the file type is .scr to be able to run avoiding blocking malware, etc. and it does some things that your common or garden screen saver doesn’t do. It isn’t a digitally signed application and the avast File System Shield (FSS) runs the emulator process would see this as suspect. Hence the win32:Malware-gen, a generic signature that is designed to detect new previously undetected variants. This is a fine balance of catching new variants or detecting good files.

So the file needs to sent to avast for analysis.

See http://www.virustotal.com/file-scan/report.html?id=0ddc11aaaeadce0ba74dab32248f0549c2c88fe2a5c8531148312b06889d351b-1301775326, whilst there are a number of detections, avast and gdata (amounting to 1) and the others are also suspicious/heuristic detections.