I created a solution using the previous VS now I have opened this Solution in VS 2010 and this reference seems to be incorrect:

It was fine before and the program has been running ok everyday for a couple of months; so why is the VS 2010 telling me this?
In the Solution Explorer it looks like something is wrong with the reference. Was fine before:

Ok – I’ve just deleted the reference above then found this build (which looks exactly the same) and added it and all seems good in the World now!

I recently installed the new
VStherefore I believe it also installed the newest version of the.NET framework. So I suspect when I opened this project it was pointed at a more recent framework version which has caused a problem with the reference.I deleted the broken reference and added it back in and it seems fine now.