the simple solution would be to use "User Input" as Attribut type for Currency Custom Attributes.
Before that I have used default "User selects from dropdown" as Attribute type for Currency - it is kind of strange to use it that way, isn't it? But there is no validation for this kind of error yet. So be carefull what you choose.
The logged error was:
javax.servlet.jsp.JspException at com.jada.taglib.language.OptionsCollection.doEndTag(OptionsCollection.java:80)