I looked at the site in IE7 and here are some things you should please try. After each step, please look through a real IE7.(not an emulator).
1) Please remove from the code the this plugin: (it does not exist physically but is referenced in the code). Please check that this isn't hardcoded into the header.
2) The image below doesn't exist but is referenced by the code. please place it in the folder or remove from code for now. Extra errors muddy the water especially when dealing with IE7.
3) Please remove the 4th image in the slider. the one of the cat.and a fishing bowl.
I looked at the code, and the IE7 problem is caused by some plugin/custom-modification which the already unstable and unpredictable IE7 interprets as taking random parts of the code and inserting them into the menus.
If you feel that its worth spending the time on the 1.2% of web users who continue using a defective 6 year old browser with well documented back-doors every hacker is aware of, then I would recommend plan A. The second plan, Plan B, would in my view be a better decision, equivalent of warning an amateur fisherman not to go fishing on a leaky boat during a hurricane (which is what IE7 is).
Plan B - Offer visitors a choice to install the Google Chrome frame which is a quick download that runs in the background allowing IE7 to 'see the web' with the eyes of a modern browser (or better yet, to upgrade) . However, if Plan B is not an option, then :
Plan A - Would involve quickly setting up a sub-domain on the same server - dev.bozofishing (for example). Then a fresh WordPress install, along with installing the latest version of Abundance. After checking that the Theme works properly running on the sub-domain on IE7 (as on the kriesi.at demo as well as my locahost), please begin adding the plugins and customization one at a time from the live site while keeping an eye on IE7..
Plan A cont..At some point you will locate the culprit when IE7 breaks. After removing the defective customization, a quick switch of the virtual directories between the live and the dev sub-domain will result in zero downtime. Plan A could be accomplished in a couple of hours, depending on which customization causes the error and the ease of replacing it.
On a side-note , Australian ecommerce sites started adding a 6% service charge for shoppers who use iIE7 (http://echoweb.com.au/wp-content/uploads/2012/06/kogan-internet-explorer-7-tax-popup.jpg )
The site looks great, by the way, in all modern browsers that I tested it in, and after looking at it for so long, I am going fishing next weekend.
This ( http://pastebin.com/6M2Zi3du ) is the IE7 code dump. If you save it on your desktop as test.html , and open it using Google Chrome (it crashes firefox), you will see the site as IE7 interpreted it.