Hm, that is annoying, yes..
I know there was a similar case with that theme some time ago, but I cannot find the thread.
My first guess is that you have added something with "hidden" formatting. Please do not paste from Word or similar editor. This might be useful
Try to remove the last post you added, and see if it returns to normal - then you know where the problem is, at least.
This might help
Even if your sidebar is not at the bottom, but in fact seems to be gone, give it a go.
I checked your blog in firefox, opera and safari. Looks the same in all three.