I guess you will know yourself that that behaviour may be not a GTK problem, but be caused by very buggy code somewhere in your application. With C it is very easy to produce such bugs, and it is really hard to find the sources. I can remember, more than 10 years ago I had a similar problem with Ruby-GTK, leading to random crashes. I can not remember if it was my wrong code, or more an issue of Ruby bindings, but it was not a GTK issue.