I viewed the tut and it worked fine for me, but I played around and I was able to reproduce your problem two (2) ways. I got scattered Pattern Along Path objects,
1)By
not converting the

Rectangle shape to a

Path object.
2)I converted the Rectangle to a pattern (>Object >Pattern Object to Pattern)
I suggest you try the following please.
1. Create the

Skeleton Path you want your pattern along first, this will make it the lowest path in the Z-order (stacking order of objects)
Note: Your skeleton path should be a simpler path, creating a wild multi-node, with alot of curves/angles in it will lead to a blotched effect, regardless if you follow the steps in the tutorial it will look messy.
2. Create a tall thin

Rectangle Width:2.0, Height:30.00 px, to resize the rectangle I suggest using the

Selector Tool's Control Bar W: and H: fields (this bar is just above the canvas area).
3. Convert the Rectangle to a Path >Path >Object to Path (Shift+ Ctrl+ C).
4. Select both objects on your canvas, then open the >Extensions >Generate from Path >Pattern Along Path... menu, using the settings below i had no problems achieving the edit as outlined in the tutorial you referenced.
Copies of the Pattern:_____Repeated
Deformation Type:________Snake
Space between:___________0.0
Normal Offset:____________0.0
Tangential Offset:_________0.0
Pattern is vertical:_________unchecked
Duplicate the pattern...:____unchecked
5. Once you get this to work then you can proceed to an object of 5 multicolored 'grouped' paths for step 2 above