Thanks everyone for your input. I purchased the step in Canada - I'm pretty sure its the original step - it has a green top and purple risers. I'll have to check to see if I kept the receipt. I probably didn't, as I didn't expect I would be having this problem.
I use the step almost daily, but at 135 pounds, I don't think its my weight causing the problem.
Its so frustrating trying to find decent workout equipment in Canada. I think if I want a better quality step, I'll have to order from Cathe's store, because the step she sells on her website is not available where I live.
Anyways, thanks again for your input.