Is S1 incompatible with S1 PRO???

Hi, I’m a beginner here, so please bear with me. Please help me figure out my problem…

I am working on a small project with 2 XBEEs on two Parallax Basic Stamps. I’ve downloaded some sample code so on Stamp 1, you push a button and on Stamp 2, a LED and buzzer sounds. With each push of the button the buzzer pitch changes higher (and as stated the LED lights). Simple code.

With 2 standard S1’s the code works as it’s supposed to.

Here’s where it gets weird:

When I swap out the standard S1s to Pros, the code works, but it’s slightly off. The pitch change for the buzzer no longer works. The buzzer only sounds at one constant pitch.

If I power down change the Xbees BACK to standard S1s, the code works as intended.

If I change out ONLY the sending Stamp to a Pro, then it acts up again.

If I change out ONLY the receiving Stamp to a Pro (and the sending unit is a standard Xbee), it works fine.

Any thoughts why this might be happening?

Could be a power issue. But then again I don’t know what pins you are working with or what commands.