I had the same problem at one point, and I think I fixed it by reducing the width of either the "bPosts" class or "bSideBar" class. For whatever reason, IE seems to add a pixel or two of extra margin between these items, causing them to not fit within your layout if the sum of the two widths is the same as the width of your layout. If you reduce the size of one of them just a bit, they should fit.

but I think it was ok last week, don't know what happen!

Welcome to the world if CSS. IE is really a pain in the arse when it comes to columns. The fastest way that I know of to fix this is to go through your css file(s) and count the width of every column that you have, make sure that all of the columns, when next to one another don't exceed the maximum width that you've specified in the 'main' or 'body' or 'wrapper'. And that *should* take care of it.

It looks like you're using a variant of b2Kubrick, so be sure that the sum of the column widths doesn't exceed the '760' specified in 'wrapper'. You could test this theory quickly enough by bumping the width of 'wrapper' to 800 or so. Just don't forget to change that value back to '760' when you're done.

As for last week's results, my best guess is that you had your browser set to a larger window size last week.

I had this same frustration with some of my custom skins (which I hope to complete and post for all soon). I figured out that if I limit my browser size to 800 x 600 and make sure that the skins display properly at that setting, then when the skin is opened in a 'larger' browser they work well.

In your main CSS file for Kubrick look for the following...
#bSideBar {
margin-left : 545px;
padding : 20px 0 10px 0;
width : 190px;
font-size : 1em;
font-family : 'Lucida Grande', Verdana, Arial, sans-serif;
}

Try reducing the "margin-left: 545px" by couple of pixels at a time, click refresh in IE and I think it will slip into place befor you take off more than 5 pixels.

Worth a try