Mail Inbox / Message Display Problems

[RoMoBo]

Wondering if anyone has some advice for just-started Apple Mail problems. (POP accounts, 10.7 Lion.)

Problem #1: I can't consistently open a message (new or read): instead of body content, I get "Loading ..." with spinning circle. No consistency here - a message that I could read before now shows "Loading...".

A quick web search mentioned Mailbox / Rebuild; which I did and introduced Problem #2: Inbox has lost almost all my mail except for recent items.

Web searching mentioned deleting com.apple.mail, which I did but had no effect on the listed Inbox messages - most have vanished.

FWIW, I've run Disk Utility (from the startup volume) but it didn't report any disk errors.

Any Mail-specific repair suggestions? TIA. -R