No sharepoint access to a VIP user

This took a little longer than expected as we had to dig deeper into the issue to understand the root cause.

I understand that the user was migrated and recreated in the domain.

Things to Find Out :
 Was the User account deleted from the domain?
 Was the same User account recreated later?
 Did we follow any process to migrate the user?

Possible Scenario :
If the answers to top 2 questions are YES, then this is what might be happening
 When the User account was delete, references still remained in the Content Database in the form of SIDs
undeleted.
 Later when the same account was recreate in the domain, the account took up the same SID from the old
account name.
 But this SID is not correct one as actually the user for the SID is deleted per the database records.
Resolution:

 KB Article for reference  http://support.microsoft.com/kb/982949

stsadm.exe -o migrateuser -oldlogin Domain name\Old user name -newlogin Domain name\New user
name –ignoresidhistory