Internet Explorer Compatibility Issue

We have a website that has issues with IE compatibility and IE functionality. The site uses a Rockettheme template (mixxmag) and has a lot of third party advertisements. There are two serious problems that need to be resolved... Problem One: People are getting kicked out of the site if they view it in IE. The messages say "internet explorer has encountered an error and needs to close" or "bad request." This does not happen in firefox. Problem Two: The site looks different in IE, and many of the features of the template are not visible when viewed in IE (6, 7 or 8). We need it to look the same in IE as it does in Firefox. This is a rush situation as everyday the site is losing viewers and advertising dollars based on these issues (especially problem #1). Please respond if you have done something like this before and can get this issue resolved quickly and for a fair price. It may just be as simple as adding "defer" calls to each script, but we are not sure and don't have time to figure it out right now. We just want it done. PM if you need more information.