Ocorreu um erro

Enquanto sua ação era processada, ocorreu um erro interno. Por favor notifique o professor.
Veja abaixo os dados do erro:

<B>Data do erro: </B>09/04/2009 23:38:33

<B>Mensagem: </B>null
<B>Classe: </B>class java.lang.NullPointerException

<B>Requisição:</B>
<B>URI = </B>/aulas/OpcoesLista
<B>QueryString = </B>null
<B>ParameterNames = </B>quest1723 || quest1722 || quest1721 || finaliza || toDo || quest1720 || testar || quest1724 ||
<B>Protocol = </B>HTTP/1.1 &nbsp; <B>Method = </B>POST

<B>Cliente:</B>
<B>HeaderNames = </B>host || user-agent || accept || accept-language || accept-encoding || accept-charset || keep-alive || connection || referer || cookie || content-type || content-length ||
<B>host = </B>www.academos.com.br
<B>user-agent = </B>Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.9.0.8) Gecko/2009032609 Firefox/3.0.8
<B>accept = </B>text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8
<B>accept-language = </B>en-us,en;q=0.5
<B>accept-encoding = </B>gzip,deflate
<B>accept-charset = </B>ISO-8859-1,utf-8;q=0.7,*;q=0.7
<B>keep-alive = </B>300
<B>connection = </B>keep-alive
<B>referer = </B>http://www.academos.com.br/aulas/OpcoesLista?toDo=resolverLista&
<B>cookie = </B>JSESSIONID=D52F4F034B22AE72C08FE71967580324
<B>content-type = </B>application/x-www-form-urlencoded
<B>content-length = </B>396
<B>Locales = </B>en_US || en ||
<B>RemoteAddr = </B>201.83.125.118
<B>RemoteHost = </B>201.83.125.118
<B>RemoteUser = </B>null

<B>Servidor:</B>
<B>ServerName = </B>www.academos.com.br
<B>ServerPort = </B>80
<B>ContextPath = </B>/aulas

<B>Pilha de Execução: </B>
java.lang.NullPointerException
at com.aulas.gerinterface.OpcoesLista.efetuaResolucao(OpcoesLista.java:796)
at com.aulas.gerinterface.OpcoesLista.action(OpcoesLista.java:108)
at com.aulas.modelos.Servlet.performTask(Servlet.java:84)
at com.aulas.modelos.Servlet.doPost(Servlet.java:46)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:709)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:802)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:252)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:173)
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:213)
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:178)
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:126)
at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:105)
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:107)
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:148)
at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:869)
at org.apache.coyote.http11.Http11BaseProtocol$Http11ConnectionHandler.processConnection(Http11BaseProtocol.java:664)
at org.apache.tomcat.util.net.PoolTcpEndpoint.processSocket(PoolTcpEndpoint.java:527)
at org.apache.tomcat.util.net.LeaderFollowerWorkerThread.runIt(LeaderFollowerWorkerThread.java:80)
at org.apache.tomcat.util.threads.ThreadPool$ControlRunnable.run(ThreadPool.java:684)
at java.lang.Thread.run(Thread.java:619)