Views are Blank

Question

Mail Version 2.1 (752/752.2)
Have an imap and a pop account.
Often, the views of both are blank and the timer icon seems to be frozen. After a while, if I click on something else, the views become populated.
Also, on many occasions, if I observe the Activity Viewer, I see that it says, for example, evaluating "x" of "y" messages, but when I review my messages, I have fewer than "y" messages.

Answer 1

Not sure of the meaning of what you see in Activity Viewer. Do you see anything there that would indicate that rules could have a bearing on this? If so, try disabling all your rules and see whether that helps.
What’s the capacity and space available on the startup disk?
Verify/repair the startup disk (not just permissions), as described here:
The Repair functions of Disk Utility: what's it all about?
After having fixed all the filesystem issues, if any, and making sure that there’s enough space available on the startup disk (a few GB, plus the space needed to make a backup copy of the Mail folder), try this:
1. Quit Mail if it’s running.
2. In the Finder, go to ~/Library/Mail/. Make a backup copy of this folder, just in case something goes wrong, e.g. by dragging it to the Desktop while holding the Option (Alt) key down. This is where all your mail is locally stored.
3. Locate Envelope Index and move it to the Trash. If you see an Envelope Index-journal file there, delete it as well.
4. Move the “IMAP-” account folder to the Trash. Note that you can do this with IMAP-type accounts because they store mail on the server and Mail can easily re-create them. DON’T trash any “POP-” account folders, as that would cause all mail stored there to be lost.
5. Open Mail. It will tell you that your mail needs to be “imported”. Click Continue and Mail will proceed to re-create Envelope Index — Mail says it’s “importing”, but it just re-creates the index if the mailboxes are already in Mail 2.x format.
6. As a side effect of having removed the IMAP account folder, that account may be in an “offline” state now. Do Mailbox > Go Online to bring it back online.
Note: For those not familiarized with the ~/ notation, it refers to the user’s home folder, i.e. ~/Library is the Library folder within the user’s home folder.