Hello Peter and Ricardo,
While I do not know if this is the exact problem that Ricardo is having, this is what I have noticed. There appears to have been a change in jQuery and how they calculate the mouse position. I noticed that in my own project, the cell under my mouse would only highlight halfway down the cell. I’ve forked another fellows fiddle to demonstrate.
http://jsfiddle.net/tMNN3/
As you can see, within the body tag I’m creating a black boarder at the top of the page. Now move your mouse over the cells. Half way down a cell, it will finally select. If you remove the CSS block and or change the pixel height to 0 the cells select properly.
Likewise, if you keep the css block as is and just change the version of jQuery from 1.9.1 to 1.8.3, then you will notice the cell selection works as desired.
-David