Folder being processed

When attempting to download your mail, you may receive an error message that says "This folder is being processed. Please wait until processing is complete to get messages." There seem to be a variety of things that can cause this. Some are listed below, with links to threads offering further details and possible fixes.

• Messages with bad headers or header fields left blank.
• Checking multiple accounts while filtering mail between accounts.
• Simultaneously getting mail for two or more accounts that use the global Inbox. In Thunderbird 0.8, it may be possible to avoid this problem by clicking the "Get Mail" icon in the toolbar rather than using the keyboard shortcut (not yet confirmed).
• Your anti-virus software locking up your Inbox.
• Checking mail while compacting folders for the account(s) being checked.

To find more Mozillazine forum threads on this subject, do a search for "folder processed" (both terms).