> Well - before we go hire someone to help us solve our problem, I will
> ask once more if someone has a solution to our problem.
>
> Firebird 2.1.3 SS running on a Debian Linux 64 bits 12 Gb RAM.
> Database is some 25 Gb.
> There are up to 100 active connections.

super server on a multi core? have you locked the CPU down to one?
Why aren't you using classic?
Do you have the TCP connections set to limit?
Is there anything in the server log?
There's no garbage collection going on at these hanging times?
Have you monitored your ram useage? I did have a problem with 2.1.3 with a
memory leak (fixed in 2.1.4 snapshot) where transliterations of blob fields
in the monitoring tables was causing a memory leak and the server would
crash and kick everyone off - not sure if exactly the same behaviour is
displayed in linux.

Alan