wiadmin is the web interface administration area. This is the area where you configure your metaframe servers, dmz settings, client deployment etc. It is a very user friendly interface. To access wiadmin, type in the url to your web interface and when you get to the login screen you will see the following url
Clear everything after MetaframeXP/ and type in wiadmin
You will be prompted to login to the web interface (You can do all of this at the web interface server by going start>programs>citrix>management consoles>web interface (Presentation Server) but as I don't know how you normally access your server, we'll do it this way)
Once authenticated, you will be in wiadmin.
I don't use Web Interface for internal access to resources, but only use it with Secure Gateway for external users.
If this has only just started happening, try and find out if anything has changed on the network eg, MFServers IP address, NAT changes on Firewall etc. I have seen this error before, and I can't remember the resolution. It sounds like a NAT issue, check that port 1494 is NATing to your MF server. I'm afraid I need more info on your current setup to be able to offer any more assistance.
Regards, Darren