MessageManager

I am deploying a commerce site and am in the test stage.
The commerce site worked fine but i needed to change
Currency References in order to match our back-office
system.

I am now getting the following error on the Order Creation
pipe:
*******************
Error Type:
Commerce.MessageManager (0x80004005)
Language "STG" does not exist in this MessageManager
instance.
/websales/include/std_util_lib.asp, line 501
************************

The error points to the following line / s in the file:
***************************
sSign = mscsMessageManager.GetMessage("currency_sign",
sCurrency)
tmpCurr = mscsMessageManager.GetLocale(sCurrency)
***************************

The default currency for ecommerce was "GBP" but i am
trying to change all references to "STG"

The st_util_lib.asp is obviously referring to a currency
setting somewhere - how can i find / edit the value ????