From a quick look, the dropdown is absolute positioned, and you put in logo image on top of original site header pushing the whole thing down.
You can adjust the position of the drop down part of menu, OR use image replacement technique for site title and keep the same height.
What is the image replacement technique. YES, this happened after I uploaded a logo. Should I adjust the header code for the placement of the image?
The theme is not hosted here at WP.ORG repo, so I can’t see the original unedited theme, but I am fairly certain that you should use image replacement technique to replace site title (text) with logo image.
example
http://thinketg.com/3-methods-for-css-image-replacement/
The height of logo should be the same as original site title text so that it won’t push menu down. However, if really necessary you can still adjust the position of dropdown.
example
#dropmenu ul { top: 26px; } /* was 0.5em = 6px */
