Your first option should be to use a decent client-side testing system. "The page could not be displayed" is totally unhelpful, therefore either:
- Don't use IE
OR
- Turn off "Friendly" error messages
It might give you some insight.
If you're still having problems, you may want to consult your network administrator to find out what the problem is, and/or your sysadmin who may have some setting set on your workstation which is making this fail.
My first guess is that you have Windows firewall or something enabled - again, talk to your network admin or sysadmin, they should be able to help.
Mark