[originalscottyg]

Try this...
Go into slip mode, then click once on the ruler format in the upper left of the edit window. I.E. if you are in Bars/Beats, click once on the Bars/Beats box just to the left of the rulers in the edit window. This should toggle the gridlines on and off. If that's not it, then I'm not sure what it might be. But I have definitely been bit by this one a couple of times.