Was there a recent upgrade or licensing change? With the implementation of Perpetual Licensing, Microsoft has rolled into GP a number of modules like Fixed Assets and Multi currency, which used to need to be purchased a la carte. With this change, companies upgrading to this licensing model receive registration keys that enable these features.
It is possible to disable Multi currency management in GP. Mariano Gomez has a great post describing the process.
dynamicsgpblogster.blogspot.com/.../effects-of-disabling-multicurrency.html