"A newer version is available" error

Question

A little background: I have a SharePoint farm with 2 web front ends load balanced, a application server and a database server, serving content to over 600 users. 
I've started experiencing some issues with users on shared accounts. For ease of use (though I don't like it) a number of staff at certain locations all login with the same user account. We use roaming profiles to maintain consistency between the computers and these shared profiles are mandatory. The internet explorer temp files are not redirected and are stored locally. 
These staff members regularly have to update a specific excel spreadsheet in a document library in SharePoint. The shared accounts are not allowed access to SharePoint for tracking and security reasons. So users log into SharePoint using their own credentials. 
Lately I've been having an issue of when they open a document and check it out to make edits they get a bar at the top that says "A newer version is available. To modify this workbook, open the latest version or save a copy." 
I've verified that it's not been checked out and had the user attempt to check this document out and they still get this error. It seems to be random and possibly per different computers. 
I first suspected it was an internet explorer caching issue and adjusted setting to clear the cache on close and to check for a new content on every visit to the page. That didn't seem to make a difference. 
We're in the process of rolling out IE 7 and I suspected maybe that would solve this issue, but we're still having the problem. I've also tried repairing and reinstalling office 2007 to no avail. I have the latest service packs and hot fixes on Office 2007 and Windows XP. I haven't upgraded SharePoint to service pack 2 yet but I do have the latest infrastructure updates on it.
I’ve seen a little information from searching around on Google but nothing specifically similar to this that has more of an answer then “reinstall office”. Does anyone have any insight into these errors and how I can go about solving them? Thanks!

Answer 1

I’m not clear from the 2 posts what should be deleted.
One says:
Deleted the registry hive \Software\Microsoft\Windows\CurrentVersion underneath
HKEY_CLASSES_ROOT\Software\Microsoft\MasterAggregatorForIPP\OleDbHandlers\{E1D2BF40-A96B-11d1-9C6B-0000F875AC61}.
The other says:
HKEY_CLASSES_ROOT\Software\Microsoft\MasterAggregatorForIPP\OleDbHandlers
{E1D2BF40-A96B-11d1-9C6B-0000F875AC61} System
Does that mean delete the key \{E1D2BF40-A96B-11d1-9C6B-0000F875AC61} or the values underneath it? And where does System come into play? I don’t see that in the registry on the PC’s I’ve checked.
I’m not sure how \Software\Microsoft\Windows\CurrentVersion relates to HKEY_CLASSES_ROOT\Software\Microsoft\MasterAggregatorForIPP\OleDbHandlers
{E1D2BF40-A96B-11d1-9C6B-0000F875AC61} System
Thanks.