My app behaves differently when purchased through Google Play!

I have just published my first app in Google Play.

When I "bought" it, it installed fine and ran as expected. However, when I try to move it to my SD card, the button is greyed out.

I developed it using Eclipse and it worked on various emulators (Android 2.2, 4.0.3 and Galaxy Tablet), with each allowing the SD card option. My manifest file has android:installLocation="auto" and my min sdk is 8 with a target sdk of 15 so there should be no problem. If I email the apk file to my phone and install it, it allows me to move to SD card, ditto to my wife's different model phone.

Is Google Play trying to eliminate SD cards, or is there something simple I'm missing? I've opened a ticket with their "support" group but, so far, I've only received emails telling me to check their FAQs!

Has anyone experienced this problem? Any suggestions would be welcome!

OK. I just got a response from Google.

I had published my app as copy protected and so it can't be copied to SD card. I need to remove the copy protection and implement licensing.

I think this thread can be closed.

Thanks Jeremiah. This was the response from Google, also. I am now looking at changing from copy protect to licensing. It's a pretty small app anyway, but I think all apps should have the SC card option where possible.