Let LU realise that user data has changed

Hi all!

I'm sorry for disturbing you lot at your noble work, but I have a small 
problem with integrating LU into my project and I hope you can give me a 
quick hint to solve the problem.
I hope I can explain it as short as possible:
I'm using LiveUser 0.15.1 and LU-Admin 0.2.1 as I'm a bit afraid of the 
work needed for migrating to the new version ;)
I have a page with several user groups. The side navigation contains 
different menus depending on the user group (e.g. user is group A -> 
menu A is rendered, group B -> menu B etc.).
A logged in user can execute a function which causes his group 
membership to be changed. My problem is that LU somehow does not realise 
this membership change which causes the wrong menus to be rendered (the 
membership is changed without no problems because logging out and in 
again results in the correct menus to be displayed). My first thought 
was to use "logout" and "login" but here's the problem that I use MD5 
encryption and I cannot simply use getProperty('passwd') for the login call.
So the question is if there's a function which i could use to "refresh" 
LU which i have overseen. Maybe there's a little error in reasoning at 
my side aswell. If so, I would really appreciate you to drive me into 
the right direction ;)

Many thanks in advance


Dennis