Hi, the reason is that input "Check rates and availability". Since you are using tables, it will expand if the content is too big. That input is too big and as ar esult the table is expanding. If you could ditch the tables, that would be the best bet, or perhaps apply a fixed width to the input.
Also as for the image at the bottom of the right column being chopped off, it's b ecause you have a fixed height on ".sidecontent". It's causing it to be a bit too short to fully show everything. You shouldn't have a height on it anyway. Remove it, or set it to min-height if you REALLY want it. However min-height won't work in IE7 :).