On the server machine I do have a init.ora, but it does not have a local_listener parameter. There is no such file on the client side.

The listener.ora on the server machine is like this:

# LISTENER.ORA Network Configuration File: C:\oracle\ora817\network\admin\listener.ora
# Generated by Oracle configuration tools.

LISTENER =
(DESCRIPTION_LIST =
(DESCRIPTION =
(ADDRESS_LIST =
(ADDRESS = (PROTOCOL = IPC)(KEY = EXTPROC0))
)
(ADDRESS_LIST =
(ADDRESS = (PROTOCOL = TCP)(HOST = dx06smt3)(PORT = 1521))
)
)
(DESCRIPTION =
(PROTOCOL_STACK =
(PRESENTATION = GIOP)
(SESSION = RAW)
)
(ADDRESS = (PROTOCOL = TCP)(HOST = dx06smt3)(PORT = 2481))
)
)

SID_LIST_LISTENER =
(SID_LIST =
(SID_DESC =
(SID_NAME = PLSExtProc)
(ORACLE_HOME = C:\oracle\ora817)
(PROGRAM = extproc)
)
(SID_DESC =
(GLOBAL_DBNAME = decasp.dx06)
(ORACLE_HOME = C:\oracle\ora817)
(SID_NAME = decasp)
)
)

The Global name, SID, Oracle home and Host entries are all correct.

What really surprises me is that, as I mentioned before, the problem happens more often on a client machine where I have the Web Server of my application and not on the other Win32 client machines.

Thank you!!