[Theme: Tidy] header height issue

Hi everyone, I’m a long time reader, first time register/poster.
You guys have gotten me out of quite a few debugging nightmares but this time, my issue seems to be so specific that I can’t find any help in existing threads.

To start, here it my site:
http://www.ktaupload.com

I am using the Tidy theme.

The issue I’m having is that when the window is resized to 600px wide or less, the header jumps from its normal height (117px) to over 900px!
This is obviously a major design/function issue and needs to be addressed.

When resizing the window back to over 600px wide, the header stays the same ridiculous height until the page is refreshed.

I will gladly provide access to any of my code to anyone that is willing to assist.

Thank you so much for any help at all. I’ve been debugging for days and have yet to have any luck.