any chance you edited the Script task template itself?
i got the same error, but I knew it was me.
i edited the template for Visual Studios C# Script task, so that the main function was not so generic, but had a proper try{}catch{} block and a few other trivial enhancements.
eve though i used a darn good text editor, and saved it with syntax correct and everything, i got the same error as you...i ended up having to revert back to the original template, and had to give up on customizing it to my liking.
your error seems so similar, i would recommend replacing the templates from another machine and see if that fixes it.
in my old example, i was opening this zip, i think, editing the ScriptMain.cs:
i was doing something wrong, whether i used the wrong zip utility to re-zip, or something else crross checks the contents, it onyl worked halfway for me.
C:\Program Files (x86)\Microsoft Visual Studio 9.0\Common7\IDE\ProjectTemplates\CSharp\SSIS_ScriptTask\1033\Integration Services Script Task.zip
Lowell
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