Support Alert: Do not delete SimConnect.dll 
 
 

It has come to our attention that some FSX customers are experiencing intermittent problems with add-ons not working when using the SimConnect interface.  This might be seen through the loss of add-ons appearing in the Add-on menu or the obvious discontinuity of functionality between the add-on and FSX.
 
We are actively looking at this problem, and have tracked it down to a NT_STATUS_CONNECTION_RESET in the low level connection layer of the Operating System.
 
Although we do not yet have a solution for this problem, we do know this is not related to an improper or incomplete installation of the SimConnect server with FSX.  PLEASE DO NOT MANUALLY DELETE THE SIMCONNECT.DLL ASSEMBLY FROM THE WINDOWS SIDE BY SIDE DIRECTORY!  We have seen posts in the forums alluding to the fact that this might solve the problem, but not only will this NOT solve the problem, you are more likely to incur additional problems by trying to manually delete this file.  If you feel strongly about re-installing SimConnect or any other portion of FSX, please use the "Repair Installation" option from the FSX program setup file on your DVD:  setup.exe.

Correcting the intermittent connection problem will likely require an update of the SimConnect dll, which will be installed as part of an update to the FSX program.