500 Internal Server Error

[DefaultExternalContentManager] returned an error. The underlying error was a org.fcrepo.server.errors.GeneralException The message was "Error getting http://gams.uni-graz.at/cocoon/toHTML?source=http%3A%2F%2Fgams.uni-graz.at%2Farchive%2Fobjects%2Fcontext%3Afercan.dcd.nehalennia._dea_e______len%2Fmethods%2Fsdef%3AObject%2FgetMetadata&style=http%3A%2F%2Fgams.uni-graz.at%2Ffercan%2Ffercan-context.xsl&model=Context&locale=de&mode=&context=context%3Afercan.person.dcd%21context%3Afercan.dcd.nehalennia._dea_e______len" .

org.fcrepo.server.errors.HttpServiceNotFoundException: [DefaultExternalContentManager] returned an error.  The underlying error was a org.fcrepo.server.errors.GeneralException  The message was  "Error getting http://gams.uni-graz.at/cocoon/toHTML?source=http%3A%2F%2Fgams.uni-graz.at%2Farchive%2Fobjects%2Fcontext%3Afercan.dcd.nehalennia._dea_e______len%2Fmethods%2Fsdef%3AObject%2FgetMetadata&style=http%3A%2F%2Fgams.uni-graz.at%2Ffercan%2Ffercan-context.xsl&model=Context&locale=de&mode=&context=context%3Afercan.person.dcd%21context%3Afercan.dcd.nehalennia._dea_e______len"  .  
	at org.fcrepo.server.storage.DefaultExternalContentManager.getExternalContent(DefaultExternalContentManager.java:155)
	at org.fcrepo.server.access.dissemination.DisseminationService.assembleDissemination(DisseminationService.java:684)
	at org.fcrepo.server.access.DefaultAccess.getDissemination(DefaultAccess.java:452)
	at org.fcrepo.server.access.FedoraAccessServlet.getDissemination(FedoraAccessServlet.java:734)
	at org.fcrepo.server.access.FedoraAccessServlet.doGet(FedoraAccessServlet.java:441)
	at javax.servlet.http.HttpServlet.service(HttpServlet.java:617)
	at javax.servlet.http.HttpServlet.service(HttpServlet.java:717)
	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:290)
	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
	at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:368)
	at org.springframework.security.web.access.channel.ChannelProcessingFilter.doFilter(ChannelProcessingFilter.java:109)
	at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:380)
	at org.springframework.security.web.FilterChainProxy.doFilter(FilterChainProxy.java:169)
	at org.springframework.web.filter.DelegatingFilterProxy.invokeDelegate(DelegatingFilterProxy.java:237)
	at org.springframework.web.filter.DelegatingFilterProxy.doFilter(DelegatingFilterProxy.java:167)
	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:235)
	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
	at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:233)
	at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:191)
	at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:127)
	at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:102)
	at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:109)
	at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:298)
	at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:857)
	at org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.process(Http11Protocol.java:588)
	at org.apache.tomcat.util.net.JIoEndpoint$Worker.run(JIoEndpoint.java:489)
	at java.lang.Thread.run(Thread.java:750)
Caused by: org.fcrepo.server.errors.GeneralException: Error getting http://gams.uni-graz.at/cocoon/toHTML?source=http%3A%2F%2Fgams.uni-graz.at%2Farchive%2Fobjects%2Fcontext%3Afercan.dcd.nehalennia._dea_e______len%2Fmethods%2Fsdef%3AObject%2FgetMetadata&style=http%3A%2F%2Fgams.uni-graz.at%2Ffercan%2Ffercan-context.xsl&model=Context&locale=de&mode=&context=context%3Afercan.person.dcd%21context%3Afercan.dcd.nehalennia._dea_e______len
	at org.fcrepo.server.storage.DefaultExternalContentManager.get(DefaultExternalContentManager.java:184)
	at org.fcrepo.server.storage.DefaultExternalContentManager.getFromWeb(DefaultExternalContentManager.java:326)
	at org.fcrepo.server.storage.DefaultExternalContentManager.getExternalContent(DefaultExternalContentManager.java:149)
	... 26 more
Caused by: java.io.IOException: Request failed [503 Service Unavailable]
	at org.fcrepo.common.http.WebClient.get(WebClient.java:211)
	at org.fcrepo.common.http.WebClient.get(WebClient.java:136)
	at org.fcrepo.server.storage.DefaultExternalContentManager.get(DefaultExternalContentManager.java:172)
	... 28 more