Empty Guild?
Every guild has a different version of it on each server. If all players of a guild move to a new server, they start building up reputation for that guild on -that- server, thus you have to rebuy every single upgrade. If you jump back to the old server, the settings should be the same as when you left.
Allright, thank you for the help EndlessDreamer
Yea, a guild exists across all servers simultaneously so guild chat, roster and message of the day work across all servers. Only the influence and upgrades are specific to a particular server.