Why would a .sln solution file open and appear empty in Microsoft Visual Basic 2010 Express – i.e. no windows showing projects and code files etc.
When I inspect the file in a text editor, it contains references to vbproj files (which are present) which indicate that it should not appear as empty.
No error messages are reported when the file is opened.
Update:
(To illustrate my problem)
It attempts to load the projects that belong to the solution:

And then results in a bare solution screen

The answer is that the projects did load for the solution but the Window to display them was not open or visible. To make it visible, go to the View menu and select Other Windows:
This displays the 4 projects referenced by the solution
Forgive me for blurring the project names but this might be commercially sensitive and therefore not for public awareness. But you get the picture.
In summary it was my lack of knowledge about the tool, though I had looked under the Window option first thinking along these lines, but the View menu is actually where one would go to display things about the project.
Thanks to everyone for your contributions.