Apple Mail compromised?

I use Mail 6.2 (1499) on OSX 10.8.2.

For a few days now, two odd things have happened.

First, when I click on a inbox which is showing a new mail counter, the messages pane is completely blank: no new mail, no existing mail. It takes literally 1 or 2 minutes before it populates. The same happens on all four accounts. It's not the mailservers as the four accounts use three different mailservers and there are no delays when accessing on my iPad or iPhone.

Second, I've been receiving spam from junk mailboxes but with real friend's names in the From field. The email accounts are different every time. I know that could be a virus or hack at their end, but in those cases the mailbox is normally their real one, and it's happened with several different names.

Anyone seen anything similar? Any theories?

Can I reinstall mail without reinstalling OSX? I know my data will be safe (and I have TM backups on two different drives), but I'd rather avoid the hassle of losing all my settings if I can.

Additional info on this one:

Outgoing mail is also delayed. It sits in the Outbox before being sent anything up to several minutes later, and when you delete mail from an Inbox the counter likewise only updates later.

Thanks. I have everything on facebook set to friends-only, so no-one should be able to access anything, but I guess if a facebook friend's account were open, that would enable the same thing.

The mail delay thing is driving me nuts, but it's a hugely busy time so the idea of reinstalling OSX and losing all my settings is not a prospect I relish.