I have precisely the same problem on a Ubuntu 10.10 server with a full installer install. The message in the logs is
ERROR [org.springframework.extensions.webscripts.AbstractRuntime] Exception from executeScript - redirecting to status template error: 00010004 Login failed
org.springframework.extensions.webscripts.WebScriptException: 00010004 Login failed
at org.alfresco.repo.web.scripts.bean.AbstractLoginBean.login(AbstractLoginBean.java:75)
at org.alfresco.repo.web.scripts.bean.LoginPost.executeImpl(LoginPost.java:73)
at org.springframework.extensions.webscripts.DeclarativeWebScript.executeImpl(DeclarativeWebScript.java:235)
at org.springframework.extensions.webscripts.DeclarativeWebScript.execute(DeclarativeWebScript.java:64)
at org.alfresco.repo.web.scripts.RepositoryContainer$2.execute(RepositoryContainer.java:377)
at org.alfresco.repo.transaction.RetryingTransactionHelper.doInTransaction(RetryingTransactionHelper.java:381)
at org.alfresco.repo.web.scripts.RepositoryContainer.transactionedExecute(RepositoryContainer.java:436)
at org.alfresco.repo.web.scripts.RepositoryContainer.transactionedExecuteAs(RepositoryContainer.java:466)
at org.alfresco.repo.web.scripts.RepositoryContainer.executeScript(RepositoryContainer.java:263)
at org.springframework.extensions.webscripts.AbstractRuntime.executeScript(AbstractRuntime.java:333)
at org.springframework.extensions.webscripts.AbstractRuntime.executeScript(AbstractRuntime.java:189)
at org.springframework.extensions.webscripts.servlet.WebScriptServlet.service(WebScriptServlet.java:118)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:717)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:290)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
at org.alfresco.web.app.servlet.GlobalLocalizationFilter.doFilter(GlobalLocalizationFilter.java:58)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:235)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:233)
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:191)
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:127)
at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:102)
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:109)
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:298)
at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:852)
at org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.process(Http11Protocol.java:588)
at org.apache.tomcat.util.net.JIoEndpoint$Worker.run(JIoEndpoint.java:489)
at java.lang.Thread.run(Thread.java:619)