My datacenter is looking to upgrade our Windows 2008 servers to Windows 2008 R2 to solve a couple issues that currently require patches that take longer to install than it takes to just do an upgrade. They’ve been hesitant to upgrade the SharePoint farms because, according to them, SharePoint is some kind of voodoo app that gets angry if you don’t properly care and feed it according to the written Word. So, I pointed them to an internal single machine farm that is used for testing and SharePoint newbies to get their feet wet in the 2010 version.
The upgrade went very smooth, and after I was given the machine back the first thing I did was go on and try to access Central Admin.
Could not load file or assembly 'Microsoft.IdentityModel, Version=184.108.40.206, Culture=neutral, PublicKeyToken=31bf3856ad364e35' or one of its dependencies
Searching on that error pointed me to the following blog post by Sensoft2000: http://sensoft2000-sharepoint.blogspot.com/2010/06/could-not-load-file-or-assembly.html
Looks like the solution is to install the Windows Identity Foundation.
After the install, everything seems to be working fine so far. Will update if I find anything else.