Figure out why my app works great in chrome/safari/firefox but not in IE7/IE8/IE9

As the title says, I have a standard web 2.0 type application, written in ruby on rails with the normal development models, etc. For some reason, it refuses to work right in IE, but works perfectly fine in other browsers. Formatting is wrong, options don't work, etc... generic rendering issues, most likely, but we don't have the time or patience to sift through all the CSS/javascript/etc and figure out what the problems are. This is a very small project for someone who knows their stuff, so we're looking for a fast completion time. Someone else (who unfortunately didn't have time to do the job) told me it's probably just a few lines of css or javascript that's causing the problem, but I'll leave the final verdict up to the winning bidder. You will not be given the source code or a zip file/archive of our code, for security reasons. You will have web-based access to the app so you can see for yourself and troubleshoot that way. We will define successful completion as you delivering to us a list of changes and line numbers/files where the changes must be made in (with the changed html/css/javascript). Don't give us a big archive of updated files. What we want is something like "on line 235 of [login to view URL], change X to Y" or, "on line 500 of [login to view URL], change A to B". We will implement and test that your changes fix the problem and that chrome/firefox/safari AND IE7/8/9 all work well without the bugs we described above, and without new bugs caused by your changes.