"Users50" within in the "Mozilla" is now called "Profiles." This will
only affect new instalations. Profiles which are now in "Users50" will
not be affected. Obviously, this will not affect Unix because there is
no "Users50" dir. When you make a new profile, it will be put in "Profiles."
If the thought of having two profile dirs bothers you, it can be fixed
by hand.
Mac - Just move the contents of Users50 into Profiles. Done.
Windows - After moving the contents from Users50 to Profiles, you can
replace all occurances of Users50 with Profiles in Mozilla\registry.dat.
Do the same for each prefs.js in each profile dir.
Sorry about this. The name Users50 was very unpopular and I got the
complaints. Let's hope Profiles is better loved.
-Conrad