mysqldump: table doesn't exist

Today I needed to dump a database, nothing special, until mysql dump growled a "table <x> doesn't exist when using LOCK TABLES", ran a check

~$ mysqlcheck -udb_user -p database_name

but everything showed up fine... then I thought "well lets not lock it...", so this worked for me:

~$ mysqldump --skip-comments --add-drop-table --skip-lock-tables --user=my_user --password=my_password database_name >> db.sql

This database in particular was imported by copying files, I fixed the permissions and owner and it is working fine otherwise so I don't know what could be causing this problem which is why I dont count this as a "fix" but just a workaround, wiser folks may understand better what is happening and enlighten me.