Evolution: Summary and Folder Mismatch

[mhinton539]

I've begun seeing the following error message from evolution mail whenever it checks for mail, or when I select or move away from the main Inbox:

Error while Storing folder 'Inbox'.
Summary and folder mismatch, even after a sync

...and sure enough, as I browse through Inbox, I notice that the message pane and the summary pane get out of sync as I go. (Rather disturbing when they are: if I hit Delete now, what will be deleted? The message highlighted in the summary, the message displayed in the message pane, or something quite else?) Hmmmm...

What would be the cause of this? I've been using Evolution a while, and this just cropped up recently. (As an emergency measure, I'm temporarily using Kontact.) And how do I recover from this regrettable state of affairs?

Thanks for hints or help!
--Mark