Odd behaviour with LOCK TABLES

[David Lombardi]

Hi All,
I have a rather weird behaviour if I issue a LOCK TABLES (I am using C API for sake of completeness).

There is one process (thread) that open a single connection and insert into several tables, found in several databases. The tables are all MyIsam and the databases are all owned by a single MYSQL instance.
The process implements a sort of hot backup of the tables in a database while inserting into the other tables.
It does this by:
- issuing LOCK TABLES on all interested tables (read lock)
- FLUSH TABLE
- copy the tables
- UNLOCK TABLES

Right after locking the first table, any other insert (on different tables) fails with the message:
"Table 'xxx' was not locked with LOCK TABLES".
Clearly, 'xxx' is not locked because it does not have to.

I am running MySQL 5.0.16-nt on Windows XP SP2.

Thanks
David Lombardi