Select all the verts, envolke the move tool and in the attribute editor for the move tool (you might need to double click the move tool Icon) theres an option box checked (with the text keep individual positions, or something like that, i think its the only one checked)

Uncheck this, select the snap to grid (or hold down x) and then move, the verts should then all align in a nice straight line.

P.S Remember to recheck the option box after you have aligned the verticies.