Are you trying to scale/rotate a single vertex? Remember that a vertex has no mass, which makes scaling or rotating a single vertex pointless/not possible. Give us a screenshot, might help.
Ello, I need a little advice on whats probably a daft problem I'm having in Maya 2008. My scale and rotate manipulators turn grey and inoperable at times, move will still work on the selected vertex's, (verticies?) but scale and rotate wont. Have I/am I doing something daft. thanks in advance and sorry again