I encountered an issue while implementing searchanise for a client's shop with the Ultimo theme and I figured I'd share it as Ultimo is quite a popular theme.
Basically what happened was that the drop down suggest appeared with a transparent background, making search result undistinguishable. I mucked about turning things on and off to find the culprit. It turned out to be the styles-ie.css that broke the layout and I did try to wipe the css file clean but it still broke things so I removed it from the layout and moved it's css declarations to the styles-ie8.css file and after that it works. I'm not sure I can say exactly why so any informed guess is welcome :)
<!-- CSS for IE --> <!-- MOVED CONTENT OF styles-ie.css TO styles-ie8.css CAUSE IT BREAKS SEARCHANISE --> <!--action method="addCssIe"><css>css/styles-ie.css</css></action--> <action method="addItem"><type>skin_css</type><name>css/styles-ie8.css</name><params/><if>lte IE 8</if></action>