XML Parsing Error: mismatched tag. Expected: </ADMINNICENAME>?

Does anyone know what file this appears in? I’m completly lost for finding it. 🙁

can be seen at: http://paintballrss.com/feed/

Full error:
XML Parsing Error: mismatched tag. Expected: </ADMINNICENAME>.
Location: http://paintballrss.com/feed/
Line Number 21, Column 32: <dc:creator><ADMINNICENAME></dc:creator>
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