Adding contributions doesn't work for certain currencies
This was curious, so I tracked it down.

Apparently the list of valid currencies predates the civicrm_currency table.  So right now the valid currencies are hardcoded - you can see that in &lt;civiroot&gt;/CRM/Core/Pseudoconstant.php around line 1077 - the currencyCode() function.

As a quick workaround, you could add your currency to the list.  However, the correct solution would be to modify this function to return the result of SELECT name FROM civicrm_currency.