Hi Matthias,
As it says in the sticky thread about important skin changes, you need to add this to your css, you can put it in stylemojo.css:
.pagelayout .addcontent{float: left; margin: 0 0 20px; }
.pagelayout .panelayout { clear: both; margin: 0 0 20px 0; padding: 0;}
.pagelayout .panelayout h2 {text-align: center; margin: 0 10px 10px 0;}
.pagelayout .regularpanes{margin: 0 auto; width: 630px; clear: both;}
.pagelayout .pane{float: left; clear: none;margin: 20px 0 20px 0; position: relative;}
.pagelayout .layoutcenter{margin: 20px 30px;}
.pagelayout .layoutalt1,
.pagelayout .layoutalt2{float: none;clear: both; width: 190px; margin: 0 auto; position: relative;}
.pagelayout .altlayoutnotice{margin-bottom: 20px;}
.pagelayout .panelistbox{position: relative; width: 190px;}
.pagelayout .pane select {width: 170px; margin-right: 10px;}
.pagelayout .layoutbuttons{right: 0; top: 5px; position: absolute;}
.pagelayout .layoutbuttons input{display: block; margin-bottom: 10px;}
The artisteer-greenlagoon skin already has this and it looks correct to me on the demo site in pagelayout.aspx
ps mojoPortal 2.3.6.4 was released today.
Best,
Joe