Upgrading my server from v1.7.5 to v1.7.7, whitelist activated, I could not connect to my server with the error message telling me I was not whitelisted, while my nickname was in the ops.txt file.
Playing around with it, I noticed that the UUID generation is based on nicknames (-un-salted hash?) and that they were case-sensitive
The problem is that v1.7.5 forced lowercase nicknames in ops.txt and white-list.txt, effectively overwriting them in that way.
The only way I could generate correct UUIDs was to edit ops.txt and white-list.txt files prior to the upgrade to v1.7.7 in order to restore the correct case of all involved nicknames.
Then, and only then, upgrade to v1.7.7 creates correct UUIDs and operators/whitelisted members can happily join.