I ran into the same problem after an automatic OS update.

I was able to get eManager running again by following the following steps:

Goto C:\WINDOWS\Microsoft.NET\Framework\v2.0.50727
and run the foolowing commands to decrypt your web.config file

aspnet_regiis -pd "connectionStrings" -app "/MyApplication"

MyApplication must be replaced with your application folder, and copy encrypted web.config to inetpub\wwwroot path.

I was having this error because y wanted to re-encrypt one new file web.config.
I did it copying to inetpub\wwwroot my not encrypted file and also copying this file to inetpub\wwwroot\MyApplication
and encrypt the new file running this command:


aspnet_regiis -pe "connectionStrings" -app "/MyApplication"