Just got my hands on a copy of Flanker 2 as well (been looking for long enough!) -so I have been reading up.
Apparently 2.5 is not compatable with the 2.0 training missions.
You need to download them (+ some more) in a different format that is compatable with 2.0.
It is something like a 118MB download from
http://www.Flanker2.com