.Net assembly version mismatch

After a few check-ins and auto merges (on TFS) of an ASP .NET Web App, I have an assembly version mismatch:

Assembly 'Telerik.Web.UI, Version=2009.3.1314.35, Culture=neutral, PublicKeyToken=121fae78165ba3d4' uses 'System.Web.Extensions, Version=3.5.0.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35' which has a higher version than referenced assembly 'System.Web.Extensions, Version=1.0.61025.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35'

Apparently, this means I should reference System.Web.Extensions version 3.5.0.0 instead of 1.0.61025.0.

I've removed and added the refer开发者_运维知识库ences to both assemblies multiple times, I've made sure there's no 1.0.61025.0 in the Web.config, I've also scanned the bin folder for anything that looks like System.Web.Extensions, but I can't find anything.

What am I missing?

Make sure that your project is targeting .NET 3.5 and that there aren't any other assembly references to System.Web.Extensions 1.0.61025.0 in your project or bin folders.