DLL Compilation Error (ASP.NET)

We have a webserver with two versions of the AjaxControlKit on it. Im getting the following error when hitting certain pages on a specific web application.

The type 'AjaxControlToolkit.CalendarExtender' exists in both 'c:\Windows\assembly\GAC_MSIL\AjaxControlToolkit\3.0.30930.28736开发者_运维问答__28f01b0e84b6d53e\AjaxControlToolkit.dll' and 'c:\Windows\assembly\GAC_MSIL\AjaxControlToolkit\3.0.30512.20315__28f01b0e84b6d53e\AjaxControlToolkit.dll'

The web project Im running has a reference to the x.30930 dll, and it also has

<add assembly="AjaxControlToolkit, Version=3.0.30930.28736, Culture=neutral, PublicKeyToken=28f01b0e84b6d53e"/>

Specified in the web.config.

For the life of me I cant find out why it wants to try running x.30512.

Any suggestions?

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Aaargh there was a reference to it in the 'global' web.config (in the c:\windows\microsoft.net\ folder