We just recently updated our .NET client to 4.5.2 and received a call from a user who was attempting to edit External Contacts through OWA.  I was able to duplicate their experience.  Both computers have the new .NET 4.5.2 installed and are using Internet Explorer 10.  If you open OWA through Firefox, the slowness issue disappears.  We are running Exchange Server 2010 SP2.  Any help would be greatly appreciated.

Hi,

Does this issue occur on only one user?

I suggest to upgrade IE t the latest version to check this problem.

Best Regards.

I was able to duplicate the problem on my machine.  So no, the problem is not isolated to one machine.  If we launch the OWA portal through a different browser though we do not experience the issue. 

Our standard IE version is 10, I can't just upgrade it to the newest version because that could break other applications the user needs in order to do their job.  Any other suggestions?