What is the error message you get?
Also I have looked at *.mbp backups, and the good news is that it is a simple text file with items like:
Code:
BEGIN:VCARD
VERSION:2.1
N;CHARSET=UTF-8;ENCODING=QUOTED-PRINTABLE:Buddy's;Name - name
TEL;CELL:XXXXXXXXXX - phone number
EMAIL;INTERNET;PREF;CHARSET=UTF-8:email@something.com - e-mail
EMAIL;INTERNET;CHARSET=UTF-8:
EMAIL;INTERNET;CHARSET=UTF-8:
X-IRMC-LUID:00020000001D
END:VCARD
So if you have a lot of phone numbers it will last a while, but at least you can restore by hand your contacts...