I delete all but zen and Tmobile zen.
My guess is the OP deleted the Dimension zen theme. In my post I recommend leaving all themes that have "Dimension" in them.
Also, if you delete the theme that is currently in use on the BB then you may get the "vanilla" (black/white) theme on reboot after removing everything. Either make sure you switch themes to the one you want to keep before making the changes or use the swiss army knife icon to change themes if you get the black/white theme.