Hi Stuart,
this is what I did:
the pgm you need to gdb is not lazarus but startlazarus.
To find that, I used:
find / -name startlazarus 2>/dev/null
Once you found it, cd to that directory and then run 'gdb startlazarus'.
I did that and submitted the result, but so far no answer.
But you need not despair completely:
The exception seems to happen whenever you open the dialog in a directory where you don't have write access. If you have created your application UNDER your home directory, the dialog will open in that directory and you are OK. However, if you then try to open parent directories until you have reached your home, then Laz will crash again. Once this exception has happened, Laz is dead and you need to kill and restart it.
I am a newcomer to Linux und dabble just like yourself, but I have reasonable experience with Delphi.
The bug that concerns us here initially put me off Laz completely, but since I found how to work around it, I have already converted several Delphi programs to Laz which I am now happily using daily under Ubuntu.