Why am I getting an 'Invalid Server Certificate' error when retrieving email even though I have the 'Verify Certificate' setting disabled?

I'm trying to configure my phone to sync with my work email account. I'm accessing it through OWA (Outlook Web Access). With the default settings, when the phone attempts to retrieve incoming mail, I get an error stating that there is an 'Invalid Server Certificate'. This persists even if I disable the Verify Certificate setting. Why is that? How do I avoid the 'Invalid Server Certificate' error? I do not receive the error if I set 'Use secure password' to Never. But, that doesn't seem too safe. Would that mean my password is sent in plain text? I'm running Android 2.3.3 on a Droid X.