HTTP Connection error: 500
<!DOCTYPE HTML PUBLIC "-//IETF//DTD HTML 2.0//EN">
<html><head><title>500 Internal Server Error</title></head><body><h1>Internal Server Error</h1><p>The server encountered an internal error and was unable to complete your request: <br><br><pre>com.bowman.xml.XMLConfigException: Character reference "" is an invalid XML character.
at com.bowman.xml.XMLConfig.<init>(XMLConfig.java:66)
at com.bowman.xml.XMLConfig.<init>(XMLConfig.java:35)
at com.bowman.xml.XMLConfig.<init>(XMLConfig.java:78)
at com.bowman.cardserv.web.WebBackend.doPost(WebBackend.java:338)
at com.bowman.httpd.PseudoHttpd.handleHttpRequest(PseudoHttpd.java:170)
at com.bowman.httpd.PseudoHttpd.access$000(PseudoHttpd.java:19)
at com.bowman.httpd.PseudoHttpd$HttpConnection.run(PseudoHttpd.java:352)
</pre></p><hr><address>Java PseudoHttpd Server 0.4.5</address></body></html>
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what can i do to solve this problem ?