Hmmmmm....

Try heading to the Character Select screen and clicking the "Addons" button in the lower left corner. Does the mod show up in that list?

If not, then the mod wasn't installed into the proper place:

The folder should be:

WoW/Interface/Addons/GuildBank

And in that folder should be the two files:
GuildBank.toc
GuildBank.lua

If it DOES show up in the list, then you must make sure that you're trying to get your file from WoW/WTF/Accounts/AccountName/SavedVariables/GuildBank.lua



--
It's all in the reflexes.