My other half and I share Outlook Express and have 4 identities altogether. The problem is that I am receiving all of his mail in my inbox (he also receives it). Our e-mail accounts don't even use the same server - his uses the mail account tied to his ISP and mine is from my business website. The other two identities are unaffected.
Could this be anything to do with problems we had recently with our ISP (virgin24/7)? Virgin had us adjust some connection settings and this is when the problem started. The password verification notice is also shown twice on dial-up.