while messing around boredly with XoloX I figured this one out. Double-clicking in the download trasfers (TransferpannelTop), Downloads (FilesPanelTop), or shared files (Building Index: ...) where a file is not present (blank space) an access violation occurs as it sends what I assume would be a null value to the double-click handler for the window.

This is easily repeatable, and probably just as easily fixed.