At 11:37 PM 16/06/2009, you wrote:

>Yes, it's an internal raid 5 disc array.

That still doesn't answer the question of whether your drive F: is physically connected to the computer that is hosting the Firebird 1.5 server.

>Additional information about the scenario:
>
>I'm using the superserver version of the firebird 1.5.5.4926. Both, the
>client and the server, are not firewalled. The client library version is
>2.1.0.17735. I have no error in the firebird log. I tried with a new empty
>database and it's the same. In the server I get connected but form a client
>pc i got the error.

Very likely the server, being v.1.5.5, has the v.1.5.5 client in the system path, and the correct Microsoft runtimes for v.1.5.5.

>Using Wireshark ( <http://www.wireshark.org> www.wireshark.org) i sniffed
>the network and found some internet protocol errors from the client pcs:
>Header checksum: 0x0000 [incorrect, should be 0x7854] [Malformed Packet:
>FB/IB GDS DB]. The same clients pcs can connect to the windows 2003 server 32bit without any error.

Can't figure that out, sorry.

>For testing purpose, I installed the Firebird 2.1 64 bits on the same server and everything works fine with that version, but right now I can't migrate the database to 2.1.

Well, you obviously have a protocol mismatch. "For testing purpose", did you consider replacing the v.2.1.1 client library on the remote machines with the v.1.5.5 one? It begs the question of why you gave the v.2.1 client library to the remote users at all.

./heLen