Unable to open Office files on SharePoint 2010 sites on Windows Server 2008 R2

Question

Setup: Windows SharePoint Server 2010 sp1 on Windows Server 2008 R2 (hosted on VMWare VSphere ESXi 5.1)
Secured using Domain SSL from GlobalSign.
Client OS: Windows 7 Professional 32bit & Windows XP SP3 32 bit
Browsers: IE10, IE9,IE8
Office: Office 2010, Office 2010 sp2 (both 32bit), Office 2007
Problem Description: Only recently, users started having issues with opening Office files (Word, Excel) on SharePoint sites. When you click on an Office file e.g. Word Document, it comes up with the option to select "Ready only" or "Edit"
and choosing either options and re-entering the login credentials results in the
application hanging. If you leave it for a while (about 5 minutes) sometimes the file opens and other times it gives the error "Could not open https://portal.com/XXX/XXX/Document.docx". Even when it opens, it's extremely
sluggish and can't do anything other than end it via Task Manager. Same with excel files. 
This happens to all the users all different OS and browsers.
On XP Pro SP3 w/ IE8, when you click on the file, the login prompt keeps popping back up repeatedly and if you click cancel, the file loads up anyway but no way of saving back onto the SharePoint site.
IMPORTANT: One exception is when logged in as a Site Collection Administrator, it
works like a dream bizarrely!!!! Opens, Edits and saves back fine on the SharePoint site.
Have tried following:
1. Repaired Office 2010 Pro; Uninstalled/Re-installed Office 2010 Pro
2. Reset Browser, unticked automatically detect proxy settings.
3. Emptied OfficeOfflineCache on Client
4. Removed WebDAV from the SharePoint server
5. Added Antivirus folder exclusion (We use SEP 11) on the SharePoint Server
Note: PDF files opens fine for all users.
I would immensely appreciate if anybody has got any advice/pointers/suggestions. Desperately out of ideas at the moment.
regards,
Compter Sez No!

Answer 1

Hi,
According to your description, When you try to open a Microsoft Office document from a SharePoint 2010 site in a client application, the document opens slowly and you are prompted to enter your credentials multiple times.
This issue may be because of SharePoint Web Front End (WFE) server(s) has Antivirus software installed and the exceptions are not set correctly.
I recommend to remove the antivirus software or set the correct permissions for the antivirus software to resolve the issue.
To configure the antivirus exceptions, please follow the guidelines in the below articles:
KB943620:
Folders to exclude when you perform a file-level antivirus scan on a server operating system.
KB952167:
Certain folders may have to be excluded from antivirus scanning when you use a file-level antivirus program in SharePoint.
KB943556:
Recommended file and folder exclusions for Microsoft Forefront Client Security or Forefront Endpoint Protection 2010.
Best regards.
Thanks