I've meanwhile downloaded wowintro.avi and tested with that (at the same desktop-resolution as you use). The only possible way to get that movie on a "screen-filling"desktop without cropping (in either panscan or movie mode) is to distort its ratio to 4:3.
I changed the "target" in my windows-shortcut into:
"C:\Program Files\Webteh\BSplayer\bsplayer.exe" "D:\Movies\New\wowintro.avi" -ar=4:3 -pan -deskmode -hide
Could you test on your system (with and/or without -pan).
P.S.: Perhaps also check settings of the several "remember"-options like concerning "movie window size" and "movie window position".