This is a bug that's been bugging me (pun intended) for a while, but I could never place my finger on what exactly what was going wrong. I've finally figured it out; if the cursor is over a button or other widget and it gets "sensitized" (i.e. gtk_widget_set_sensitive is called on it with TRUE) while the cursor is still on, the user can't click on it until he moves the mouse out and back in. Since it's a little hard to explain, I've posted some sample code. Try clicking on the button more than once; you'll see what I mean. Also, sorry if this has been reported before, I couldn't find it anywhere else.