Why does Windows Explorer not recognise Visual Studio 2010b2 solution files?

(No actual programming involved, hence posting here instead of SO.)

A couple of days ago I installed Visual Studio 2010 beta 2 on freshly installed Windows 7 box. This has never had VS2010 beta 1 installed.

I've just checked out my code from Subversion (which was last run in VS2010 beta 1), and tried double-clicking on the solution file - nothing happens. The icon shows the VS2010 infinity band, but hovering over it shows Version: (unrecognised version).

I can open up the solution manually, but why does Explorer not know about the version? (Which I assume is why it won't open up via double-clicking.)

EDIT: I've just checked against a solution created directly in Visual Studio 2010 - and that one works! I've had a look in the files themselves, and I can't see any obvious differences... will keep experimenting.

EDIT: I've now blogged about this for the sake of greater exposure.

Got it!

After opening the solution manually, I added a new project (just to provoke a change) and saved the solution. There was a change to the solution file after all - I just wasn't looking carefully:

Before (broken):

Microsoft Visual Studio Solution File, Format Version 11.00
# Visual Studio 10

After (working):

Microsoft Visual Studio Solution File, Format Version 11.00
# Visual Studio 2010

So basically, the key is to change "10" to "2010" in the second line. If I still had beta 1 installed I could confirm that this really is a change, and not just me having manually mucked around with the solution file before, of course...

As you noted, there is error (or change - however you look at it) in solution file. However, I took approach of opening each solution file using "Open with" menu, manually selecting Visual Studio 2010 and then just clicking save. This will update solution file.