I found the answer.  Here is a link: http://travislaird.com/blog/default.aspx

I have copied the explanation here:

Importing lists from Excel 2007 returns a Method 'Post' of object 'IOWSPostData' failed dialog. Again, not really a problem with WSS 3.0 but rather the result of a failed Application.SharePointVersion() call in the Excel Add-In which results in Excel attempting to use the IOWSPostData.Post() method to publish the Excel range which is used with SharePoint Team Services 1.0. By forcing the version lookup result variable to 2 or greater, Excel will use SOAP to communicate with WSS 3.0 and the publish request will be successful. To make this change, open the Excel Add-In EXPTOOWS.XLA locate in C:\Program Files\Microsoft Office\Office12\1033 by default. Press Alt+F11 to display the Visual Basic code editor and search (Ctrl+F) for the line lVer = Application.SharePointVersion(URL). Comment out that line with a single quote and add the line lVer=2 so your Intialize() method should now look like this:

Sub Initialize(List, Title, URL, QuickLaunch)

strQuickLaunch = QuickLaunch

aTarget(iPublishURL) = URL

aTarget(iPublishListName) = List

aTarget(iPublishListDesc) = Title

'lVer = Application.SharePointVersion(URL)

lVer = 2

End Sub

Finally I managed to alter the XLA-fil. I work with Vista, WSS 3.0 and Office 2007, and I think all the security-stuff on Vista created access problems to the file. The file had to be copied to my Documents-folder, do the changes, and then copied back.

Well anyway, it did not do the trick for me.
The initial error message about 'Post' of object 'IOWSPostData' dissapeared, but a new one showed up:
 
"Cannot connect to the server at this time. Your table cannot be published"

Ever seen this one? I get this message when I push the “Import” button in Sharepoint.

Any solutions anyone?   

Vista/Office 2007/WSS 3.0

HeidiSitara

I changed the code as follows and everything worked immediately for MS OSS 2007 and WSS 3.0 and MS Office 2007:

<before the change>
lVer = Application.SharePointVersion(URL)
<before the change>

<after the change>
lVer = Application.SharePointVersion(URL)
lVer = 3
<after the change>

Albert VH