Friendly advice to all: Tighten up your Guild Bank access, and this does not happen. Restricting withdrawals to officers and having member level ask for stuff is a bit more work, but saves you from "new guildie robbed us blind" syndrome.

Also, keep your account information to yourself. If you feel your pass has been discovered change it! Ingame, you can type the following:

.password oldpass oldpass newpass

Whereas if I want to change pass from apples to oranges I would do this:

.password apples apples oranges

Hope that helps!