Did you happen to install an older version of Tableau Server? There was a known bug (fixed in 7.0.4) that sometimes caused the server to throw errors like yours:
Views would sometimes fail to load and the error message 'java.lang.NullPointerException' would be in the Windows Event Viewer and Tableau VizQL log files. This issue no longer occurs.
Thank you very much for your reply. It was a fresh installation. I have never installed older version.
Sorry, I personally haven't seen this error before. You might need to open up a support case. Before you do that, however it could be worth your time simply to do an uninstall and reinstall of Server. Use steps 4-6 in this article to make sure you "destroy" all old configuration information before you reinstall:
I set up another Windows Server from scratch, and installed Tableau Server on it. I still get the same error. I may have to give up, but here are my environment.
VMware ESXi 5.0
Windows Server 2008 R2 SP1 (virtual)
Any hope? Thank you.