The System Info page in the admin section will hang if JIRA is run without internet access. So will 500page.jsp, when an error occurs. This is because JIRA tries to parse entityengine.xml, and the parser tries to download the DTD (http://www.ofbiz.org/dtds/entity-config.dtd). The page will eventually load, with "Database type" and "Database JNDI address" displaying an error. Doing a thread dump when the page is hanging shows:

"http-8080-Processor23" daemon prio=1 tid=0x0828e8c8 nid=0x1a67 runnable [0x5b3d7000..0x5b3d9740]
at java.net.Inet6AddressImpl.lookupAllHostAddr(Native Method)
at java.net.InetAddress$1.lookupAllHostAddr(InetAddress.java:838)
at java.net.InetAddress.getAddressFromNameService(InetAddress.java:1176)
at java.net.InetAddress.getAllByName0(InetAddress.java:1126)
at java.net.InetAddress.getAllByName0(InetAddress.java:1098)
at java.net.InetAddress.getAllByName(InetAddress.java:1061)
at java.net.InetAddress.getByName(InetAddress.java:958)
at java.net.InetSocketAddress.<init>(InetSocketAddress.java:124)
at sun.net.NetworkClient.doConnect(NetworkClient.java:157)
at sun.net.www.http.HttpClient.openServer(HttpClient.java:365)
at sun.net.www.http.HttpClient.openServer(HttpClient.java:477)

• locked <0x45d5e758> (a sun.net.www.http.HttpClient)
  at sun.net.www.http.HttpClient.<init>(HttpClient.java:214)
  at sun.net.www.http.HttpClient.New(HttpClient.java:287)
  at sun.net.www.http.HttpClient.New(HttpClient.java:299)
  at sun.net.www.protocol.http.HttpURLConnection.getNewHttpClient(HttpURLConnection.java:784)
  at sun.net.www.protocol.http.HttpURLConnection.plainConnect(HttpURLConnection.java:736)
  at sun.net.www.protocol.http.HttpURLConnection.connect(HttpURLConnection.java:661)
  at sun.net.www.protocol.http.HttpURLConnection.getInputStream(HttpURLConnection.java:905)
• locked <0x45d577e8> (a sun.net.www.protocol.http.HttpURLConnection)
  at org.apache.xerces.impl.XMLEntityManager.setupCurrentEntity(Unknown Source)
  at org.apache.xerces.impl.XMLEntityManager.startEntity(Unknown Source)
  at org.apache.xerces.impl.XMLEntityManager.startDTDEntity(Unknown Source)
  at org.apache.xerces.impl.XMLDTDScannerImpl.setInputSource(Unknown Source)
  at org.apache.xerces.impl.XMLDocumentScannerImpl$DTDDispatcher.dispatch(Unknown Source)
  at org.apache.xerces.impl.XMLDocumentFragmentScannerImpl.scanDocument(Unknown Source)
  at org.apache.xerces.parsers.XML11Configuration.parse(Unknown Source)
  at org.apache.xerces.parsers.XML11Configuration.parse(Unknown Source)
  at org.apache.xerces.parsers.XMLParser.parse(Unknown Source)
  at org.apache.xerces.parsers.AbstractSAXParser.parse(Unknown Source)
  at org.dom4j.io.SAXReader.read(SAXReader.java:339)
  at org.dom4j.io.SAXReader.read(SAXReader.java:261)
  at com.atlassian.jira.web.action.admin.ViewSystemInfo.getDocument(ViewSystemInfo.java:267)
  at com.atlassian.jira.web.action.admin.ViewSystemInfo.getDatabaseType(ViewSystemInfo.java:90)
  at com.atlassian.jira.web.action.admin.ViewSystemInfo.getProps(ViewSystemInfo.java:78)