I'll submit this directly to support as well, but in case others are seeing this too I thought a forum post would be helpful. When I first encountered this bug I thought I had corrupted some settings in AMS and would need to re-install, as killing the process and re-launching did not fix it.
It seems that AMS is constantly checking what's in the Windows clipboard. I have some Japanese strings in an Excel file from our translators which I wanted to bring into a dialog in my AMS project. As soon as I copied the string " CD からのインストールを続行しますか？または新しいバージョンをダウンロードしますか？" , I got a popup with title "AutoPlay Media Studio" and the message "Encountered an improper argument" ... closing the dialog just results in another one, infinitely it would seem. I could only get out of AMS by killing the process in Windows Task Manager process list. Now I've discovered that if I replace the offending string in my Windows clipboard, the message will stop appearing after clicking OK 1-2 more times. Excel seemed to indicate the font was Calibri (TT).