mmswitch.ax stands for Morgan Multimedia Stream switcher. It's intended to help Microsoft Media player to support AVI with 2 audio streams, and used to be incompatible with BSPlayer, as audio stream selection is one of the many features already embedded in BSplayer code, no filter is required for this task. To workaround your issue, uninstall Morgan Switcher.
This was for mmswitch v0.94B, but I think that it's fixed now in latest
v0.96B