Initialization failed, could not load file or assembly 'system', version=4.0.0.0, culture=natural, publickeytoken=b77a5c561934e089' or one of its dependencies. the system cannot find the file specified anyone can make anything out of this ?

Does Exchange Powershell work? Have you tried just reinstalling the EMC?MVP Exchange Server

Power Shell Does Work and i can use outlook to connect to the server, OWA doesn't work how can i reinstall the emc ? i tried using the setup.com /R:MT command but got an error that MT is already installed. i think it's IIS related.

Thanks for the info, does sounds like IIS since both rely on IIS. Have a look at this and post back with your findings. http://msexchangeteam.com/archive/2010/02/04/453946.aspxMVP Exchange Server

The exchange team did crate a tool that checks that IIS has all apropriate settings. EMT Shooter which can be downloaded from here http://msexchangeteam.com/archive/2010/12/07/457139.aspx unfortantley, i can't seem to run the tool. and it resolts in an error. is there a way to re-install the EMT ?

You can run Exchange Setup again and just select Management Tools. I would suggest install Management Tools on another computer and the run ExBPA Health Check to insure everything is running properly on the Exchange box. Link for installing, http://technet.microsoft.com/en-us/library/bb232090.aspx I am still concerned that OWA is not working properly either.MVP Exchange Server

where can i find a list of the IIS dependencies settings ? for example, all the entries in the application pool should be bound to which version of .Net ? 2 or 4 ? which authentication method should i use for the OWA, etc, etc , etc i did install MT on a different computer, and it is working just fine. running ExBpa resulted in 4 critical errors all are certificate SAN mismatch, but since there is non installed i don't think it's a big deal Just FYI, after installing the MT on another machine, the MT on the original machine are working just fine.

So OWA is still not working correctly? Please turn up IIS logging to get some idea of what may be happening when trying to access OWA. MVP Exchange Server

I recently inherited an SBS 2011 machine with the identical problem - the cause that I found was that ALL the application pools in IIS had been set to use the v4.0 .NET Framework. I compared this to my reference SBS 2011 machine and all the Exchange related application pools should have been set to v2.0 of the .NET Framework. I corrected these, and a few others besides, based on my reference machine and did an iisreset and my EMC and OWA came up instantly.