I can't recall if QTP 9.1 w/ .NET add-in "technically" supports the .NET 2.0 ToolStrip class object or not.
I test against apps that have these objects, where I typically just click a button on the object. Based on object recognition, it seems like QTP does support the objects. In practice, though, I had problems where tests would very often fail on a step where the action was to click a button on the toolstrip. I can't recall for sure anymore, but the error might have been like "requested service not found." In the end, MI support was useless on the issue, and I found a reliable workaround by using analog recording for steps operating on the toolstrip class objects.