I have had success using another savegame with my own profile, I used one I found at Gamefaq, but it started out at Basic Braining
You are using the SavedGame0, SavedGame1, etc and just copying over the original saved game files right? It might also be version incompatibility, try patching Psychonauts to 1.04 or or reinstalling it to a lesser version 1.00.
I hope this helps.
Edit: Could you send me that savegame Psychonuggget gave you please. Or did he send you his whole profile? Either way, send please.
my email is posted above