What version of tyFlow are you using?
If you upgraded to tyFlow 1.100 when this problem occurred, and you're relying on particle simulation groups to control collision filtering....there was a known bug that slipped into v1.100 that results in missed collisions when particle simulation groups are used in tandem with PhysX. The fix build (v1.101) should be up later this evening, so give that a shot once it's released and see if it fixes the issue.
If you upgraded to tyFlow 1.100 when this problem occurred, and you're relying on particle simulation groups to control collision filtering....there was a known bug that slipped into v1.100 that results in missed collisions when particle simulation groups are used in tandem with PhysX. The fix build (v1.101) should be up later this evening, so give that a shot once it's released and see if it fixes the issue.