Jarkko,

Thanks for your answer.

I checked for php logs and found no errors. On the other hand, I
have this server running for as long as two years with no problems.

Neverthless, looking into the firebird.log, I found a couple of
SCH_validate error several months ago which didn't crash the server.

Another thing to answer is about the hardware. This is happening to
me in two different PCs: the old server with more than two years
running and a new one with a month or so, with the "same" database
(backed up from the old one and restored into the new one). So I think
the problem may be in the database.

Aldo