Enterprise manager 10g can not start

[theresatan]

Hi:

I just installed oracle 10g 10.1.0.2.0
when I typed

http://localhost:5500/em,

I got

The database status is currently unavailable. It is possible that the database is in mount or nomount state. Click 'Startup' to obtain the current status and open the database. If the database cannot be opened, click 'Perform Recovery' to perform an appropriate recovery operation

the exact error as thread1177-1110895, but not as luck as mashadt, I removed everything and reinstalled but the problem was still existed. I followed Mufasa's instruction, and sqlnet.authentication_services = (NTS) is on my sqlnet.ora.

I typed

http://localhost:5500/em/console/database/login

and filled in user and pw(system) connect as normal, then I got
"Io exception: The Network Adapter could not establish the connection"

I can create table, insert data to the db using SQL plus, so database is open.

Any idea?

Thanks!