WordPress seems installed, but won't let me install theme

I’ve asked the Developer of the theme I’m using, but thought I would ask here too (sorry, I’m sure the answer is here, but I can’t find it).

My client is hosting with GoDaddy.com. I’m trying to install the FlexSqueeze theme to her WordPress hosted site. After starting the upload, I get the error “Are you sure you want to do this? Please try again.” and clicking the try again just takes me back to the upload page. How do I get around this? I already had my client on the phone with Godaddy.com for 30 minutes with no resolution.

Thank you