Yeah, I had the same thing happen to me when I was working on hard, I had GG&HT 5* for a while before I could get a pass on FWD. FWD's solo is long enough and difficult enough that you have to be able to get through a fairly long portion of it without help from Over Drive to pass the song, where as the GG&HT chard is dumbed down enough that this really never becomes an issue. Practice Solos A, B, and C; if you can get past these, OD will keep you alive through solo D.
Oddly enough, the expert charts for these two songs are the opposite. Passing FWD on expert is trivial for me now, but I fail GG&HT about half the time.