how do I reconnect a mailbox from a mail store that a user was previously associated with?

After a server crash and subsequent mail store recovery using eseutil and isinteg, I was moving users to a new mailbox store I had created. Well, I started seeing consistency errors in the new databases. I had a flat file backup of the information store before I started migrating users so I restored the files and mounted the mail stores. I can see the users mailboxes with a little red x, but I cannot reconnect the mailbox to the user because the user is associated with the new mailbox store - which now has an empty mailbox. I mounted the store in the mailbox recovery center and was able to find a match for each of the mailboxes, but the reconnect option is greyed out.

I am currently running the eseutil tools on the corrupted new mailbox stores, but this is taking many hours. It would probably be better for me to reconnect the old mailboxes. Can someone guide me? I searched the internet but could not find any answers.

Thanks for any help I can get!