MapManager (Gisinternals) - INCLUDES

Does anybody have any experience with using Mapmanager to manage their MapServer mapfiles? My question is specifically about using INCLUDES in mapfiles. Since having an INCLUDE in a mapfile results in error message saying "Unable to access file. Error opening included file". Which leads me to believe it is supported and I am probably just doing something wrong.

Edit:
Tried using both relative and absolute path. The way I have my mapfiles is that I have them split multiple separate files MAP – contains the main map tags, LAYER – contains all the data, styles etc., CONFIG – contains any other potential information like db connection. MAP reads LAYER & CONFIG files using INCLUDE. By themselves it works. But when I import the MAP file into mapmanager I get the error message. Any advice or tip on how to get around this would be greatly appreciated.