When I copy "Text A" and "Text B" to the clipboard via Ctrl+C inside Visual Studio, I can paste "Text A" using Ctrl+V.
When I copy "Text A" from another application (say, a browser) and "Text B" from Visual Studio, I cannot paste "Text A" using Ctrl+V -- it is not in the clipboard ring.
My suggestion is to add text content from the system clipboard to the internal clipboard ring when Visual Studio is activated (WM_ACTIVATE), if the text is different from the topmost entry in the clipboard ring.
An extremely sensible suggestion now I see it. I know exactly what you are talking about, it happens to me fairly often when bouncing between the forum and the IDE:
Actually, the same suggestion also holds for dialogs inside the IDE, like Search/Replace: Ideally, new clipboard data would be available to the clipboard ring after leaving such a dialog.