Get rid of McAfee. It's terrible on the Mac, and is likely the cause of the problems you're having. Use whatever uninstaller is provided by McAfee... do not simply drag the app to the trash, as that will not remove it properly!
As for the malware that was found, that was extremely unlikely to be anything that would have affected your Mac. It was most likely Windows malware attached to e-mail messages in Mail, and allowing McAfee to remove it may have corrupted your mailboxes. You should rebuild all your mailboxes (select each one, one at a time, and choose Rebuilt from the Mailbox menu), and in the future, if you install any other anti-virus software (which I don't recommend), do not allow it to remove any "malware" that it claims to find! Instead, see:
How to remove infected files
For more information on this kind of thing, see my Mac Malware Guide.
(Fair disclosure: I may receive compensation from links to my sites, TheSafeMac.com and AdwareMedic.com.)