I'm trying to update a record and getting this error:

Error Message:
----------------------------------------
Unsuccessful execution caused by a system error that precludes
successful execution of subsequent statements.
Unable to complete network request to host "thalys2.personalsoft.com.br".
Error reading data from the connection.
Foi forçado o cancelamento de uma conexão existente pelo host remoto.

The error just happens in this record.
I disabled all triggers in this table.
I did a backup/restore with all options described in the IBPhoenix
document about recovering a database.
I upgraded FB to 1.5.2 SuperServer but the error was happening with
1.5.1 SuperServer too.
The server is a Windows 2000 SP 4.

Thanks.