A couple of things:
1 Web site is down for GalaticCraft - Including WIKI.
2. With GC installed ExtraUtilities mod can not access the Deep Dark or the last Millennium dimensions. I read that this has something to do with how GC reads -0 dimensions and or fake player settings. Doesn't matter as there seems to be no easy work around to fix. SO given the choice between ExtraUtilities and GC, I have to go with EU. Map reset. - Hope this issue gets resolved at some point.
Thanks for a great mod mate.