Free upgrade to NAV11 causing reboot?

I got an email this morning saying that a free update to NAV 2011 is available.  I have NAV 2010 (17.8.0.5) on XP with SP3.  When I try to download/install the upgrade, I get to the point where my current NAV tells me that "NavDownloader[1].exe is safe" (or something to that effect) and then my system reboots.  When it comes back up, Windows tells me that "The system has recovered from a serious error."  Everything seems to be working fine after the reboot but I still have the older version of NAV.  I tried it again to see if it was a fluke but the same thing happened.

 

Ideas?

 

       Dave