OK, I've wasted 2 hours on this so it time to ask for help. I opened up my latest website that I'm working on (VS 2010) this morning and whenever I access a page that uses server side code I get errors like these:

CS1061: 'System.Web.UI.WebControls.Image' does not contain a definition for 'DataBinding' and no extension method 'DataBinding' accepting a first argument of type 'System.Web.UI.WebControls.Image' could be found (are you missing a using directive or an assembly reference?)

It depends on the first control on the page as to what error I get, sometimes it is a Button click event has no defintion. I have removed the offending control and put it back it, several times to no effect.
I haven't seen this before and have no idea what the issue is. It was working when I left yesterday!!
Anyone have any ideas? Please...

Oddly, it seems to be spreading... The button control in my master page still worked this morning and now it brings up the same type of error when the site loads. Earlier, the site would load but moving to another page would cause the problem. I'm stumped:(

And, solved. Feel like a bit of muppet but shutting down my laptop worked...

Has anyone got any ideas about what happened with VS 2010 for that to happen?