The problem is in your LDAP account. All the standard disclaimers about how this could screw something up applies... (ie take a backup before trying this) but this worked on my server for a test account that I created. I have the Samba/POSIX LDAP extensions so the attributes that were on this users were the standard ones created.
First create the following file, modifying the dn: field to your user account.
Then once you have created that file (I created it as /tmp/asdf.ldif) run the following command:
If you have extra attributes that are causing an error in that command add them to the .ldif file.
ldapmodify -x -H ldapi:/// -D uid=zimbra,cn=admins,cn=zimbra -w `zmlocalconfig -s zimbra_ldap_password | cut -f3 -d" "` -f /tmp/asdf.ldif
What this does is delete all the attributes that are specific to the sambaSamAccount and the posixAccount object classes, and then removes those object classes from the account.