You're right :-)
... i've tried: it works fine !
nero 6.6.1.15c and langpack 6.6.1.15a (FR)
So if I understand, the only difference between 6.6.1.15 "a,b,c" is the toolbar include into/with the setup ? So a,b,c is the same build but with different toolbar ? No others difference like nero file being update between a,b,c build ?
(just to be sure)