FWIW, I just installed and configured this module on my ZC1.5.6-alpha test-bed. While the message about the invalid currency:

Code:
Unknown currency code specified (MODULE_SHIPPING_UPSXML_CURRENCY_CODE), using store default (USD).
does appear initially, it disappears once the module is configured. That error is simply cosmetic ... unless you have configured the UPS currency code with an unknown value, in which case the message appears similar to

Code:
upsxml: Unknown currency code specified (xyz), using store default (USD).