Try this, clearing your cache usually works for most minor problems. If that doesn't work, come back and fill out the entire template that is provided, so that I can make a more educated guess as to what the problem is. Thanks.

If that is the case(your IP changing), then it's just a matter of fixing the problem.

This is where the template comes in handy, because you haven't filled it out I have to attempt to guess at how you are configured.

If you're simply behind a firewall, one of these tutorials should help you.

However if you are using a router, then you should take a look at this post here, which will explain about port forwarding.

If you are behind a router, and you were hosting before then you have likely already done the port forwarding portion. I'm just guessing here, but from what you said I got the assumption that your local IP has changed, which would mean that the port forward is no longer valid, since it is forwarding to nothing.

What you will want to do is go to Start, Programs, Applications, and click on Command Prompt. Once in there type in "ipconfig" and hit enter.

This will display a bunch of information, you are looking for the line that says:

IP Address . . . . . . . . . . : [numbers]

Those numbers are your new local IP address. If you're port forwarded already then it's just a matter of changing the old address to the new one.

This has turned into a very long post that could have easily been very short had you filled out the template like you're supposed to, and I asked. Even if the information seems redundant or not-needed. I advise you next time to fill out the template, or I won't be as willing to help. It's not there to annoy you, it's for your own benefit to have your problem resolved faster.