You've installed mv_aseffects.vp right? Move it out of your FS2 folder. You only want that file if you play single player only.
A better soultion than just moving the file is to do this.
1. Create a folder called Multiplayer.
2. Download and unzip
this vp file in it.
3. When playing a multiplayer game choose Features>>Select Mod>>Multiplayer in the launcher. When you've finished simply click the no mod button.
If you ever update the media vp files this solution may stop working. However the problem caused by mv_aseffects.vp may also have gone away too
Just delete the file and you'll be back to a standard FS2 Open install.
For those who are wondering the VP simply contains the tables from mv_effects.