Logging into dashboard brings up old theme

I haven’t been able to duplicate this problem on the boards here.

I installed a new WordPress theme. The problem is, the new theme displays in Firefox (3.6.3) and IE 7 fine, until I log into the dashboard. When I click on “Visit site” within the WP dashboard, both browsers display my OLD theme. I have done the following to attempt to address the problem:

1. Cleared all history and cache, disabled the WP saved password info. Closed browser, re-entered. Same result.

2. Disabled FF cache altogether, repeated #1. Still no change.

Again, the new theme displays fine when I simply visit the site from the URL bar. It’s when I’m logged in and click on the “Visit site” link (which simply points to the URL) that I get the old theme.

Am I missing an obvious step here? I’ve not had much experience with this, as I’ve only used one theme since 2008.

Thanks for any advice.