Sorry, my fault! The bug is in both files, I don't know why I thought it's just in one of them.
So the problem might still occur. There's just a little problem: I made some changes to my template and now I can't reproduce it anymore ;-)
However, I know the problem was there, and therefore I tried to find out what did change between TYPO3 3.5.0 and 3.6.0.
In 3.6.0, the line looks like this:
$item = '<div id="anchorID'.t3lib_div::shortmd5($this->I['uid'].'-'.$this->WMid).'" style="position:absolute;visibility:hidden;"></div><div id="itemID'.t3lib_div::shortmd5($this->I['uid'].'-'.$this->WMid).'" style="width:100%; height:100%;">'.$item.'</div>';
3.5.0 contained this line instead:
$item = '<div id="anchorID'.t3lib_div::shortmd5($this->I["uid"]."-".$this->WMid).'" style="position:absolute;visibility:hidden;"></div><div id="itemID'.t3lib_div::shortmd5($this->I["uid"]."-".$this->WMid).'" width="100%" height="100%">'.$item.'</div>';
As you can see, Kasper has replaced some of the double quotation marks with single ones, AND he has changed the width and the height definition from HTML to inline CSS.
Could this be the problem?
Since I cannot reproduce it I'm not sure, so I suggest that we keep this bug including this information until someone has the problem again. Then we'll see.