Unable to add widgets to brand new site- likely a nonce issue?

I am using 2.9.2 and keep getting that frustrating “Are you sure you want to do this?” error when attempting to add widgets, even simple text ones.

The website is frankleonardcpa.com (and I’ve only just begun working on it.)

I did a fresh reinstall; still got the error. Deactivated, then deleted all my plugins; still got the error. Didn’t increase the size for uploads, because I’m not trying to upload anything! Tried everything I could find from previous postings- nothing is working.

I read that this is likely a nonce issue- if that’s the case, does anyone know how to fix it? I’m totally at a loss for what to try next- help is much appreciated!