Unable to load Winforms designer in VS2012 due to old assembly reference

I don't think this is anything specific to Advantage Database Server but I have recently upgrade to a new version of the Advantage .NET provider (now version 11.10.2.21).

The solution builds perfectly yet when I load certain winforms in the VS2012 designer I get the following error :-

Could not load file or assembly 'Advantage.Data.Provider, Version=11.10.2.1, Culture=neutral, PublicKeyToken=e33137c86a38dc06' or one of its dependencies. The system cannot find the file specified.

Version 11.10.2.1 was the old version that I uninstalled before installing 11.10.2.21

When I try and find the reference to the old assembly in Find (entire solution) it doesn't find anything.

Does anyone know where this reference could be located? I want to remove it so that I can continue to work on my forms.