It seems a platform related issue. On my installation( Git version) on Fedora17, the above message is always there in Terminal, but the application never crashes.
My 0.63.04 installation on windows xp works just fine and there is not message like that.
The way I get the crash is to have a tree view control open in the Params panel (e.g. the Width Point List for an Advance Outline) then click on the close icon of the canvas window to close the application while the Advanced Outline is still selected on the canvas. If the outline is not selected you don’t get the crash.
Genete knows which bug this is referring to, so hopefully it will be of use!