Ratter51, do you remember how low the readings were before you ate the grapes?
One of the complications you may be facing now is that the glimepride is pushing your pancreas to produce the insulin it can, but because your body is becoming more resistant to the effects of insulin, the mechanism within the body that calls for insulin and cuts off the supply isn't working well. Think of it a little like a sticky throttle on an engine. And when you eat sugar to react to what feels like a hypo, the amount of sugar makes a difference, too.
The standard for responding to hypos is 15 grams of carbohydrates, wait 15 minutes, retest, and then see if you need more sugar. For green grapes, 15 grams of carbs is one half cup. Eat a cup of grapes (I like them well enough to do that) and that's 30 grams of carbs, which may be enough at one time for your body to call for more insulin and you kind of end up on this roller coaster of hypos and high readings.
But props for continuing to take the glimepride. It seems to be making a real difference for you. But managing your diabetes will be, for you as it was for all of us, a matter of adjustment in what you eat, how much you exercise, etc. We're all trying to figure this out.