Solving build problems after upgrading from Beta2 to RC

If you like me did not read the upgrade manual thoroughly before trying to run your existing Beta2-builds in TFS 2010 RC you might have encountered some or all of these problems. (Upgrade manual can be found in this post http://blogs.msdn.com/bkrieger/archive/2010/02/03/tfs-2010-beta2-to-rc-upgrade-guide.aspx)

Build ends with the following error: File not found: C:\Windows\Microsoft.NET\Framework\v4.0.21006\MSBuild.exe
If you look in the Framework folder you notice that the RC of .NET Framework is in a folder called v4.0.30128 – so of course the files cannot be found.
In the upgrade guide, chapter 5 – point 3 you can read that you have to update your Build templates. It also says to create a new project and take the templates from there. One point that is not that clear in the guide is that if you create a new project in a Collection that was created under Beta2 you will get the Beta2 templates. So you will have to create a new Collection and then create a new project in that collection to be able to get a hold on the new Build templates. So the steps in chapter 5, point 2 is what you should do for the build templates as well.
I also made the obvious mistake not the check-in the new templates after adding them, so I did not find the new templates at first. Luckily I have made this error several times, so I knew how to solve it

Since we installed a complete new Build Server with the RC version we ran into the following problem as well.
When using Lab Management you have several Agents. So when configuring your builds you might point to the Build Server as described in this post http://tomasscott.wordpress.com/2010/01/09/default-setting-might-cause-problems-with-tfs2010-builds/
Remember to change that value for the build server as well as the value on the tab Build Defaults.

Enjoy the RC!