Hi,
I did a quick test, and it crashed for me once on both the included test levels. I played about 10 times in all, to give you a vague idea about frequency.
I also noticed a bunch of other issues:
On the level "step2", on one of the runs, something happened so the character would only be drawn while it was moving. Incidentally, that was a run where the program crashed.
There seemingly is no way to end or restart a level, apart from completing it or dying. At least not from the menus. This can be problematic on levels where you can get stuck, such as on the left side of the screen on "step2". The only way to get unstuck is to close the program!
On "step2", it is possible to ride on top of the monster. To do this, climb the latter, press and hold the left key, and if you hit the monster, you stay on top of it until it changes direction, or you let go of the left key.
It didn't look like an intentional feature
On my first run on "step2", the vertical position on the avatar would change when pressing the up key, even when not near the ladder. The change was erratic and small, like a faulty jump function. On later runs I detected no such behavior.
I am using Windows XP SP3, and nVidia G-Force 8800GT, driver version 6.14.12.6099.
Hope you can use the report.