Scaling problem working with AI and PS

I've created some artwork in Photoshop and want to place it behind some text I've created in AI.

The instructions I've used in the past--that always worked--were:

1) Create the PS art and then save it to the desktop as a PNG file.

2) Create the text file in AI and save.

3) Open and copy the PNG file.

4) Open the AI file.

5) Do EDIT>Paste in Back.

This should paste the PS/PNG art behind the Ai text.  It does indeed do this, but the art is way out of scale with the text--it's WAY too big.

The funny thing is, when I began this project and I did the Paste in Back, it worked perfectly.  (I created both the AI file and PS files with the same dimensions.) But then somewhere along the way, it started doing what I just described.  Anybody know how to correct this?  Thanks!