Hi Elliot,
  Could you please do the following and send me the output.  In the command window before opening the results viewer, type these commands.  The last will open the viewer itself.

global WFU_LOG
WFU_LOG=wfu_LOG;
WFU_LOG.on
WFU_LOG.level('info')
wfu_results_viewer

Then try to open your FEAT again.  When the error happens, please send the results of the LOG output.

Thanks,
Ben