After installing Service Pack 2 for Exchange Server 2010, this error message may occur when trying to access OWA and ECP unencrypted via HTTP:
"The request could not be executed. There may be security reasons or a session timeout."
This is how it can be fixed:
First check in the IIS Manager whether "SSL required" is deactivated for the OWA, ECP etc. directories
IIS Manager -> Default Website -> SSL Settings: Deactivate the checkbox "SSL required" (ONLY IF INTERNAL ACCESS IS REQUIRED VIA HTTP)
If this is the case, the web.config file under "C:\Program Files\Microsoft\Exchange Server\V14\ClientAccess\Owa" must be edited, it is best to create a backup of the web.config file beforehand
The file can be opened with Notepad, then the following line must be searched for
<httpCookies httpOnlyCookies=“false“ requireSSL=“true“ domain=““ />
This line must then be changed as follows:
<httpCookies httpOnlyCookies=“false“ requireSSL=“false“ domain=““ />
Then save the file and restart the IIS with '"iisreset /noforce". Done.