When I try to right-click on items in the Tridion content manager I get an error.
The error is inside Tridion’s own error display mechanism, showing the IP address.
Here’s a screen grab:

It’s worth noting that this is inside a Windows XP Mode VM, across a VPN to an IP address on a client network.
You need to make sure that your browser security settings are set up correctly in Internet Explorer:
From the Internet Explorer menu bar, select Tools > Internet Options.
On the Security tab, select the Internet content zone.
Click the Custom Level button and enable the following settings :
ActiveX controls and plug-ins:
Downloads:
Miscellaneous:
Scripting:
Click OK to enable these settings.
On the Security tab, select the Trusted Sites Web content zone.
Click the Sites button. In the Trusted sites dialog that appears, type the name of the Content Manager Web address, then click Add. Click Close to close the Trusted sites dialog. This setting ensures that you can access all content within a Component.
Select the Privacy tab and click the Advanced button. Select the Override automatic cookie handling option. Select the Always Allow Session Cookies option. Click OK.
Click OK in the Internet Options window.