I would recommend starting Wbemtest. Connect to \\servername\root\cimv2. Specify your credentials in domain\username format. If you can't get past this screen, try the same but for a different computer. Assuming you can get connected run a query like "select * from win32_operatingsystem". You still might try this on another computer if you've never used WBEMTest just so you can see what you should get.
I'd try this first as well as checking if you can connect to any remote machines. Then we'll know if the problem is the remote server or your machine or credentials. Is the computer you are running PowerShell on in the same domain as the remote servers? I've run into issues when using a workgroup machine to check a domain member.
Jeffery Hicks
Microsoft PowerShell MVP
SAPIEN Technologies - Scripting, Simplified. www.SAPIEN.com
blog: http://blog.SAPIEN.com