A debug log would help here, see my sig for how to create one.
Also, I'm not sure what you mean by "there is nothing in the mediavps_3612 folder when you select it in the launcher". Do you mean that you're selecting c:/games/freespace2/mediavps_3612
in the "basics settings" tab in wxlauncher? If so, then you need to select c:\games\freespace2 in that tab (then select the appropriate FSO executable) and select mediavps_3612 in the mod tab.