Why an activity is trying to open the softkeyboard? JB bug?

Why an activity is trying to open the softkeyboard? JB bug?

I have a main activity that opens another activity called popup through
startActivity(popup). popup only contains a grid of thumbnails. Before
calling popup, I hide the soft keyboard with this:
InputMethodManager imm = (InputMethodManager)
getSystemService(Context.INPUT_METHOD_SERVICE);
imm.hideSoftInputFromWindow(mytextview.getWindowToken(), 0)
This works fine. However, popup also popups the keyboard for a fraction of
a second. I don't need any keyboard in the popup activity, so I tried
adding
android:focusable="false"
in the layout of popup, and also
android:windowSoftInputMode="stateHidden"
in the manifest file where I declare the activity popup. Still, the
keyboard appears and disappears for a fraction of a second ('flickers')
before opening the grid in popup...
This problem begun when I upgraded to Jelly Bean. With GB and ICS, never
saw this. And now I see this with all keyboards. Maybe a JB bug?? (that's
why I didn't posted any code for popup).
Any clue will be appreciated.
Thanks!!
L.