I'm mildly disappointed that none of you recognised the puzzle I posted yesterday.
It's a level from Polarium, a puzzle game for the DS. In this game, tiles flip between white and black when selected. The aim is to in a single stroke without passing through the same tile twice, change the white and black tiles such that each row contains tiles of a single colour. The grey border doesn't count for this, and allows you to exit and re-enter the main block of tiles.
For example, solving the puzzle posted yesterday could be done by selecting the tiles in the following order:
The levels start off very simple, but get much more complicated as you go on. There's also a time attack mode, where new rows fall from the top of the screen and solved rows disappear (like in Tetris). I'd been meaning to get hold of it for a while since playing glasshalf_empty's copy, and spotted a pre-owned one in Game for £8 the other day. At that price it's excellent value.