I have same problem, on Vista.

wot
http://i.imgur.com/HSQva7k.jpg

Don't gimmi bullshit about updating java. And this is on a mac if you couldn't tell.

The console reads this when i try logging in:

server: emps-world.net
java.lang.NullPointerException
   at net.emps.client.model.Client.b(Unknown Source)
   at net.emps.client.model.Client.a(Unknown Source)
   at net.emps.client.model.a.a(Unknown Source)
   at net.emps.client.a.c.run(Unknown Source)
   at java.lang.Thread.run(Thread.java:745)


and proceeds to give the message in the title

Same goes for the downloadable client?

And type 'tracert emps-world.net' in cmd and paste here what it says (go to cmd at your start menu, typ cmd in search bar and press enter)

Do you have this every time. Or just sometimes?

@ Mary, this is only on my mac, and I haven't tried the dl client
@Thomy, nope, it's all the time (on the mac).

It looks like your firewall is blocking the connection then. Do you have another computer in your network to test if it works there?
Please also try to use the download client, that should work for sure.