Mail invisible after mavericks update

Question

I have upgraded my Mac Pro 2009 to Mavericks. Mail is now invisible. When I click on the icon in the dock, the application menu appears at the top of the page, but it is not possible to view anything, zoom to anything, or open any new windows, folders, mailboxes or mail. One time only, the icon in the dock showed the number of unread emails (which I read from a web email client on a different device. Since then, no mails are retrieved.
My only email account is an ISP account (not gmail etc)
Any thoughts? Thank-you, anyone, for your help.
Leon

Answer 1

Some of your user files (not system files) have incorrect permissions or are locked. This procedure will unlock all your user files, reset their ownership, and remove their access-control lists. If you've set special values for those attributes, they will be reverted. In that case, either stop here, or be prepared to recreate the settings if necessary. Do so only after verifying that those settings didn't cause the problem. If none of this is meaningful to you, you don't need to worry about it.
Back up all data.
Step 1
If you have more than one user, and the one in question is not an administrator, then go to Step 2.
Enter the following command in the Terminal window in the same way as before (triple-click, copy, and paste):
{ sudo chflags -R nouchg,nouappnd ~ $TMPDIR..; sudo chown -R $UID:staff ~ $_; sudo chmod -R u+rwX ~ $_; chmod -R -N ~ $_; } 2>&-
This time you'll be prompted for your login password, which won't be displayed when you type it. You may get a one-time warning to be careful. If you don’t have a login password, you’ll need to set one before you can run the command. If you see a message that your username "is not in the sudoers file," then you're not logged in as an administrator.
The command may take several minutes to run, depending on how many files you have. Wait for a new line ending in a dollar sign ($) to appear, then quit Terminal.
Step 2 (optional)
Take this step only if you have trouble with Step 1, if you prefer not to take it, or if it doesn't solve the problem.
Boot into Recovery. When the OS X Utilities screen appears, select
Utilities ▹ Terminal
from the menu bar. A Terminal window will open. In that window, type this:
res
Press the tab key. The partial command you typed will automatically be completed to this:
resetpassword
Press return. A Reset Password window will open. You’re not  going to reset a password.
Select your startup volume ("Macintosh HD," unless you gave it a different name) if not already selected.
Select your username from the menu labeled Select the user account if not already selected.
Under Reset Home Directory Permissions and ACLs, click the Reset button.
Select
 ▹ Restart
from the menu bar.