I was having a problem with the WP125 widget, in that it was impossible to place other widgets in the same sidebar column without having the layout all screwed up.
Looking into the coding for this widget I found that when ads were placed two by two, this was done by using CSS float: left;
The problem seemed to be that this float:left was not subsequently cleared in the widget, messing up the layouts of any subsequent widgets.
My solution was to use the ATO: Style WIDGETS facility, placing "clear: both;" in the widget container code.
This seemed to be easier than going into the code of WP125 and doesn't seem to cause any problems with other widgets I am using.
I'm posting this so that anyone who is having the same problem may be helped --- and, if someone has a better solution --- please post here.