We are sorry for your trouble, it seems as though there is actually a bug in the Adobe InDesign installer for CS5.5 for windows7 which is causing our installer not to work, you can install it manually though:
- Close InDesign
- Download and unpack this zip file (https://dl.dropbox.com/u/33037258/Mag%2B_CS5.5_win.zip)
- Place the folder under Programs
- Download and unpack this zip file (https://dl.dropbox.com/u/33037258/Mag%2BCS5.5_win_plugins.zip)
- Place the Mag+ folder inside your Adobe InDesign Plugins folder (most likely found under Programs > Adobe > Adobe InDesign > Plug-ins.
- Start InDesign and you should find the Mag+ plugin by clicking on Windows.
Let me know how it works out!