"This document could not be checked out." SharePoint 2010 checkout action using IE8

Question

I am setting up a two-server farm, and most everything works, except the checkout action for a document.  This problem occurs in both site collections, one of which requires checkout, and the other does not.
Here are the options I've tried:
Snow Leopard, Firefox 3.0.1 - works
Snow Leopard, Safari - works
Win 2003, IE 7 - works
XP, Firefox - works
XP, IE 8 - "This document could not be checked out.  You may not have permission to check out the document or it is already checked out or locked for editing by another user."
In IE8, I am able to open a document as read only then use the button presented by Word to check out the document.  I cannot use that as a workaround, as not all users have a version of Office that will allow checkout in that way.
Checkin works fine.  I need to resolve the checkout error.

Answer 1

I was having the same problem mentioned here. I noted that this problem only appears when I use the FQDN in the URL ex 'http://hostname.domain.com/default.aspx'. If I access the Sharepoint site using the URL 'http://hostname/default.aspx', then
I do not have any problems checking files in or out.
I ran into this same error pattern when trying to do a document edit (library is set to force a check out), or do a direct check out via the ribbon menu or item context menu.  Oddly enough when we would use the 'Edit Properties' ribbon button (which forces
a check out) we did not get an error and the document's status would change to 'checked out'.  Below are the two messages we would receive when trying to do a check out:
 IE error message - "This document could not be checked out. You may not have permission to check out this document or it is already checked out or locked by another user." - Click OK
 IE Error message - "The document could not be opened for editing. A Microsoft SharePoint Foundation compatible application could not be found to edit the document." - Click OK
After trying several different suggestions I realized that I wasn't having the problem when I was accessing the site locally via FQDN but only when I was using the Public Site URL (via https).  Turns out we were getting the error because we did not have
an AAM currectly setup.  Once I changed our AAM for the Internet zone with the Public URL value instead of the FQDN the error went away.
Hope this helps anyone else trying to track this down.  Oh and this was SP2010 w/SP1 (Patch version 14.0.6106.5001) on Win2008 R2 with clients running both Win7 and WinXP using IE8.