I'm on the mission Regain The Rift which is the Imperial civil war quest, it says to report to Legate Rikke but when I talk to her she does not recognize the quest, there is no option to complete the quest. What's going on? I really want to continue with the civil war quests. Help.

1.7

I've also had this problem, try reinstalling skyrim (and the 1.7 update). Fixed it for me.