Whoa, uh, why are you modifying VP files? You don't need to alter them at all to do modding - they're just containers. Do all your work in /[yourmod]/data/ and the appropriate subfolders, and only package into a VP when you want to release.
As for that error, it looks like you don't have the 3.6.12 MediaVPs installed. For Blue Planet to work properly you MUST have the following:
-A full FreeSpace 2 install
-MediaVPS 3.6.12 located in a subfolder named (DO NOT CHANGE) mediavps_3612
-An up to date Blue Planet 1 install located in a subfolder named (DO NOT CHANGE) blueplanet
-Finally, Blue Planet 2 (if you want to play that) located in a subfolder named blueplanet2
It sounds like you might be having issues with folders being in the wrong places or having the wrong names.
You should also play with a recent build. Try this one:
http://www.mediafire.com/?lc9f01f75nmp8n7If you keep having errors please generate and post a debug log as per the instructions in the Support forum. BP is totally stable when you've got it installed right but it can be annoying to get everything in the right place.