Root Can't enter debugging mode

[wrench]

GT-7510UW (white tab)

I checked the debugging option under Applications>Development, then powered off. Pressed and held Power and Volume Down buttons. I get the Samsung Galaxy Tab 10.1 screen, but instead of the two android icons immediately afterward, the screen goes black, then the Tab 10.1 screen again, followed by screen going black again. This repeats for as long as I hold the two buttons. When I release, it boots normally.

I had a 10.1 Tab before and had no problems getting into debugging mode.

 

[wrench]

OK, I got in, but had to use a different sequence:

Press the power button and volume down buttons simultaneously, and after the Samsung logo appears, release the power button and continue holding the volume down button.