While upgrading to Exchange 2010 SP2 using the GUI, you will come across the error message shown below. This only happens while upgrading the CAS role.
The reason is that the CAS requires a new pre-requisite for supporting OWA mini (a new feature in SP2). Hence, either install it using Server Manager (right click “Web Server” and add role service) or Windows PowerShell.
To install using PowerShell, run Import-Module ServerManager followed by Add-WindowsFeature Web-WMI.
Another option is to run the setup from the command line, Setup.Com /mode:upgrade /InstallWindowsComponents
Happy upgrading 
Its work in my case. But we should close the EMS console when upgrade the Exch2010 SP2 otherwise its getting error.
Thanks for the tip Jigs
I upgraded our Exchange 2010 SP1 on the weekend to SP2 with Rollup 1 – now have no Free/Busy data for Outlook clients. <9 months exp btw.
Thanks,some great data here keep up the good work. I actually allow for a more creative comment as I’m a bit out of my depth but I will be checking back here for further updates.
Regards,
Thanks Marlboro.
Or just read carefully the SP2 requirements :-)
Yesman, That’s one way of getting it right ;)
Thanks.