SQL Developer

Hello guys, so this is the thing:

I uninstalled previous installation from my laptop as it was old and not installed by me, and then I went to install full Oracle 11g enterprise edition.

My operating system is MS Windows Vista SP1.
On the page, that checks prerequisities I got one warning. It was the thing with resolving IPs through DHCP, which requires loopback device installed.

So here is my problem. I followed instructions from oracle help page http://download.oracle.com/docs/cd/B19306_01/install.102/b14316/reqs.htm#BABGCEAI
I set IP address to 192.168.40.40 and in etc/hosts I added line according to that, with one exception.
As I did not know my domain name (which I think I dont have) I left it blank.
However, everything seemed to work fine, I was able to ping loopback, or ping 192.168.40.40.
Finally, I was able to continue my installation without warnings.

After completing installation, I launched SQL Developer and started trying new connection. However, sys account, nor hr seemed to work.
I was getting that "network adapter could not establish connection" error all the time.

When I tried Sql-plus, I was able to connect to database as sysdba (or hr), and work with database.

I successfully pinged my db through: tnsping orcl

In oracle Database Control it said, that orcl database is UP.

I have absolutely no idea, how can I fix this, I googled for 3 hours now but it seems like nobody had this problem after they have successfully installed loopback device.

Two files, oracle\product\11.1.0\db_1\NETWORK\ADMIN\tnsnames.ora and listener.ora have information set correct (at least I think so), with right database name, hostname, etc...
What I am not sure about is, that in network connections manager in Vista it says, that local area network 2 (my loopback device) has limited connectivity.

Any help would be greatly appreciated. As I am new to oracle systems, maybe I am missing something obvious, but I just cant find it out. Thanks.