Yes, you can try uninstalling and reinstalling Outlook. If you do so, you should export your email settings so that you can import them after reinstalling Outlook. You may also want to export, Contacts, Calendar, etc.
But, I think I'd be inclined to uninstall your anti-virus software first and see whether that solves the problem. And, I'd also run
CCleaner before reinstalling your anti-virus software and before testing Outlook with your anti-virus software uninstalled.
If, indeed, you can not retrieve email with your anti-virus software enabled, how do you plan to utilize it? Periodically run a full scan or what? What anti-virus software are you using?
The stated requirement by the ISP of turning off anti-virus software makes no sense to me, and it doesn't sound right to robpomeroy either. Think about it. Once your email has been scanned for viruses by your ISP and is on it's way to your computer, what difference should it make whether you have anti-virus software enabled and monitoring your incoming mail?
My ISP is Earthlink. They scan all mail for viruses. That has no effect on me retrieving mail with Outlook with my anti-virus software enabled.