Ubuntu 11.10 64-bit/C/GTK 3 menu crash

I have a C program I'm working on that uses GTK. 4 options - Create New File, Open Existing File, Save File and Quit were originally just gtk buttons on the window - short cut while initially coding. Now it's improved to the point that the few things I have working so far need to go out for testing to the users that wanted it. Well, in order to clean it up I made those 4 options into a "File" submenu on a menubar. The Create New File option, besides setting an internal variable, uses a gtk_dialog to send the message

New CSS File Will Be Created With Your Changes
When You Save The File

There is newline after "Changes" - a "\n" in C, to force this to a multi-line display.

Without the newline, the message was still wrapping to 2 lines.

The message is displayed, and returns from the call to the common function I use that contains the dialogbox.

As soon as the function "returns", so control is passed back to the menubar handling (e.g., code I didn't write) the entire process aborts. I have tried this without a multi-line message and it works - it only aborts when the message text was multi-line.

I have screen captures and the source available, including the traceback, etc., in the terminal window.

I am able to work around this for now, but wonder why this aborts. Everything I've seen indicates this can be a multi-line text string.

Thanks in advance,
Dave ;)