Question : E-mail addresses missing from Outlook cache

We have an Outlook 2007 user who had a large number of e-mail addresses in his cache so when he started typing the e-mail addresses they would come up for him.  Now a good portion of them are missing including internal ones.  The only things that were done to his system recently were some new Contacts were added and some Windows updates were done.  How could this happen and can these saved e-mail addresses be recovered or they will just have to be resaved?  

Answer : E-mail addresses missing from Outlook cache

That is controlled by .nk2 file. Hope the following link can help.
http://support.microsoft.com/?kbid=287623