I am using the 11.2, express edition, on a Windows 7 machine.
Logging in with sqlplus works when I explicitly provide the username and password, works OK:

Code:
>sqlplus
..
Enter user-name: <entering..>
Enter password: <entering..>

Connected to:
Oracle Databvase 11g Express Edition ...etc.
However, it does not work when I provide the credentials in the sqlplus command:

Code:
sqlplus <login>/<password>@xe

ERROR:
ORA-12541: TNS:no listener
tnsping returns OK, so the listener is there and running.
What could be the reason for the error?
Thanks.