Microsoft Outlook can not open attachments - intermittent

Hi we recently upgraded our Exchange Server to 2013.

Since then users on Outlook 2010 and Outlook 2007 are receiving the following message when trying to open an word or excel attachment:

Cannot open file: C:\\users\dianaw\AppData\Local\Microsoft\Windows\Temporary Internet Files\Content....The file may not exist, you may not have permission to open it, or it may be open in another program. Right-click the folder that contains the file, and then click Properties to check your permissions for the folder.

The attachment will eventually open after several tries.

I have tried the following:

I have checked the permissions on the C:\\users\dianaw\AppData\Local\Microsoft\Windows folder

I have looked at cleaning out the Temporary Outlook Files folder

I have modified trusted locations in word and excel to allow sub folders.

I have tried to open outlook in safe mode in case it was an add-in that was causing the problem.

Any suggestions as users are getting frustrated.

Thanks