Omega subtheme visualization with Internet Explorer

Hi,
I'm having a big issue with Internet Explorer compatibility.

Here's how my homepage looks with Chrome (and how it should look)

and here's how it looks on IE7

I tried to "aggregate and compress CSS" under Performance, but apparently I had only the result of messing my website even in Chrome, as now the pictures in my homepage are not visible (should I re-upload my css files?).