I've just (today) upgraded this machine from 1.5.1 to 1.5.3 (classic
on fedora core 5)
and ran a program suite that was fine before. I have rebooted since as
well. There are only 2 client connections in existance. I've run it
twice and had exactly the same both times (except the number of the
lock id). At the point where a client updates a record (I think) I get
the following on the command line the C program is run from

Fatal lock manager error: invalid lock id (35368), errno: 11
--Resource temporarily unavailable

and below in the firebird.log


telensa108.telensa.com Tue Oct 3 14:23:08 2006
ISC_kill: process 2028 couldn't deliver signal 16 to process
3028: permission denied

telensa108.telensa.com Tue Oct 3 14:23:08 2006
Fatal lock manager error: invalid lock id (35368), errno: 11