A customer ran into a problem where he is getting "Method 'Post' of object 'IOWSPostData' failed" when trying to create a sharepoint list via importing a SpreadSheet using Excel. There are plenty of posts on the Internet about this and the fix is to update EXPTOOWS.XLA to force a different version number.
The original macro code uses a new method in the Excel 2007 object model Application.SharePointVersion(URL). That method is returning 0 in the customer's environment causing spreadsheet import not to work.
As it turns out, Application.SharePointVersion checks the root site for a Sharepoint site to determine the version. Because for this particular environment setup, I do not have a valid Sharepoint site at the root, it does not return the correct version number.
The solution was to create a dummy blank sharepoint site at the root of a web site and now users can import spreadsheets and create list using spreadsheets for all sites (root and sub site).