This is one of the rare issues I was facing with my farm.
Due to domain crash I have created a new domain with the same name and created all users which were there in old domain.
- After creating a new domain I have tried to connect with the old configuration database which failed with invalid user credentials issue.
- So I have created a new Configuration Database as I have Content DB of the site with me.
- PSConfig was completed successfully and attach content DB worked fine.
- Now the main issue occurred, site was accessible fine if I use farm admin credentials but it gave "Access Denied" error for all other users which I have added to the site earlier.
- From my research I found it was due to Schema mismatch, so when I delete and re add that user it worked fine.
- Or you can use STSADM -o migrateuser command