Active Filter in Groups/Latest Discussion

I installed ELGG 1.5 on April 1st and changed a PhPNuke site to a ELGG site (

The transition has gone very well, and over 500 users already made the switch.  First big glitch today.  For some reason, when you go to main groups page:

and click on Latest Discussion

it simply returns a blank page.  I have not made any changes to any code since installation and this was working fine a day ago.

Any ideas???