Ah! My Goddess: the Movie

'Oh My Goddess is the story of Keiichi, who through a small misunderstanding in wish semantics has become the proud boyfriend of Belldandy, a goddess... The Oh My Goddess movie takes place right after the 5 episode OVA series. Belldandy is visited by a man out of her past who casts a spell upon her which causes her to lose all her memories of her time with Keiichi. As if that wasn't enough, this spell also is a computer virus, of sorts, that begins the systematic destruction of the entire Goddess network.' -- from animefu.com