Do an adquery user for that user and note the UID/GID.
Now do an ls -ln on that home directory .
If the numbers are different, you have an identity mismatch. This could be due to something changing in the domain (long shot, but perhaps migrated??? or conflict with another source like local file? most likely human intervention???).
chmoding will solve the issue for that user and we provide a tool called adfixid to do this in bulk.
*** HANDLE WITH CARE ***