Crashes when using effects

Hi,

When I am using effect, (setting effect value or removing effect), Kdenlive crashes.
I have caught two occurs of this problem with gdb (zipped here http://www.kdenlive.org/mantis/file_download.php?file_id=796&type=bug).

Example steps to reproduce:
Add to timeline some clip, doesn't matter if mpeg, flv or other.
Add some effect.
Setting effect value -> sometimes causes crash
Removing effect -> sometimes causes crash
Add some effect.
Setting effect value -> sometimes causes crash
Removing effect -> sometimes causes crash
...etc.

I am running Kdenlive via usb storage live distribution. I have Intel Pentium Dual Core 2.1, 3 GB RAM and Intel GMA x4500HD.

Thanks for any ideas