Dynamic Menus Mixed [5.1.0-B2]

Imported From: http://groups.google.com/group/in-portal-bugs/browse_thread/thread/81f230719b61e380#

I have an issue with dynamic menus in v510-B2 version (updated from 503). Dynamic menus on front are completely mixed, while they appears correctly in admin structure. Priority doesn't seems to change anything. I've tried to reset menu cache unsuccessfully. What I mean by "mixed" is that submenus appears in another menu than the one they are belonging to, and others submenus doesn't appear at all.