My hero starts flying? WHY?!

Hello, everybody.

To start with, I haven't got any answer to my question in the Beginners forum, so I really hope that anyone would be experienced enough here to help me. I would appreciate any hint.

I have the following problem: I'm trying to study one of the code snippets (game templates) from our beloved AUM - air combat game where a player shoots helicopters with a rocket. I have modified a couple of things like helicopters generation and player data indication, but what I don't like at all is how the sky looks. It's simply terrible - that sky cube with standard animated sky texture.

I have found one very nice sky sphere with a texture on "Terminal 26" website and wanted to replace that awful sky cube with that nice sky sphere. I didn't change anything else - I swear.
You know what happens now? When I start my level, my hero simply starts slowly floating into the air! Getting higher and higher, verdammt noch mal! Really surprising, because the only thing that I've changed was deleting the cube and inserting that sphere into my level. I HAVEN'T changed player movement code anyhow. Here is how it looks like:

code:

---

action player_moves
{
	player = me;
	my.health = 100;
	my.invisible = on; 

	my.enable_impact = on;
	my.enable_entity = on;
	my.event = player_event;

	while (my.health > 0)
	{
		vec_set (camera.pos, my.pos);
		camera.tilt += 20 * mouse_force.y * time;
		camera.pan -= 20 * mouse_force.x * time;
		my.pan = camera.pan;	
		my.tilt = camera.tilt;
		player_speed.x = 15 * (key_w - key_s) * time - 0.5 * recoil; 
		player_speed.y = 10 * (key_a - key_d) * time; 
		vec_set (temp, my.x);
		temp.z -= 1000;
		trace_mode = ignore_me + use_box;
		player_speed.z = -trace (my.x, temp);	
		move_mode = ignore_you + ignore_passable;	
		ent_move(player_speed, nullvector);

		wait (1);
	}
}

---

Please, could anyone tell me what could be the reason for such a ridiculous model behaviour?