do...
tracert if underlying networks are different.


Usage: tracert [-d] [-h maximum_hops] [-j host-list] [-w timeout] target_name

Options:
-d Do not resolve addresses to hostnames.
-h maximum_hops Maximum number of hops to search for target.
-j host-list Loose source route along host-list.
-w timeout Wait timeout milliseconds for each reply.


tnsping the server, try using ip addresses in the tnsnames and listener files, use net8 connectivity to check connection.


doing an ipconfig on the server machine will get you the ipaddress.

also try explicitly setting the oracle sid...

Also check that the database sid(in the services menu..oracleservicexxxx) is same as actual db sid, if that's changed then you can have touble as well...

recreate the service


oradimxx -delete -sid

oradimxx -new -sid -intpwd AUTO -pfile





Hope this will get you somewhere...