There are a lot of measures proposed for "the time of recalc". Put banner on SO, increase amount of close votes, put banner on meta (already done) etc
However, there's a small flaw in this logic: there's no "time of recalc". Recalc is an event that changes rep once and forever. When the "time of recalc" ends, and all banners are removed, some users will start asking the question about their reputation again.
I think that it would be useful to put banners to userinfo pages of currently registered users, the banners disappearing after user sees them once. Userinfo is a particularly good place, because
- it doesn't draw unnecessary attention of newcomers (they don't see it)
- it doesn't mingle those who's aware of the issue (banners are private, and disappear after fist read)
- it will prevent user from asking such questions since the first place he goes to check his rep is his profile.