Good guess Pontiac, but this is a currency conversion issue. We only track 21 distinct currencies for conversion, but we'll start tracking any currency upon request. For example, we recently added the
Philippine Peso to work around this problem.
Our system uses the US dollar for currency limits for those currencies the system isn't explicitly tracking, so that's why this error crops up from time to time. I just added the Macedonian denar to our "tracked currencies" list, so you should be able to fuel-up with that currency now.
By the way, today 1 USD = 48 MKD, that's why the numbers for the default limits are so far off.