I just tried to recreate this situation.

While disconnected from the Internet, I created a Basic meeting  Workspace as a child site of an existing  WSS top-level site on my local box. I then went into Outlook and created a new meeting. I was able to view the Meeting workspace  in the browser, however, I was unable to link  to it using the Meeting Workspace tool pane in Outlook. I got the following error when I tried to add my site to the "Select a location" list  as an Other site or "Link to an existing location" by "Select the workspace":


Even though I am the box  administrator and a SharePoint administrator  on all levels, the "Select a Workspace"dropdown didn't list any workspaces. The OK button was also grayed out.

However, after connecting to the Internet, I attempted to link to the same Meeting Workspace and everything worked as expected. Could that be the problem?

If not, can you give step by step instructions to recreate the problem?

Also, from the help:
Link to existing workspace
By default, the list only shows workspaces  you created or for which you belong to the Administrator site group at the location you specified in step 1 on the task pane. If the workspace you want doesn't appear in the list, in step 1 on the task pane, select a different location. In step 2, check the list of workspaces again to see which ones are available at this new location.