The new Toolstrips and Toolstrip Containers are a great Windows Forms addition in VS2005. Toolstrips are positionable menubars working with the Toolstrip containers to be relocated on any of the four sides of a panel or form. DIVElements still has a sweeter feel with their SandBar and SandDock components, but VS2005 out-of-the-box has gained some serious UI beef.
I noticed a squirreliness with the Toolstrip Container today and finally discovered the cause. The Toolstrip Menubar would disappear. Several times it did this. Seems the TopToolStripPanelVisible property kept getting changed to "false." Changing to "true" restores the toolstrip.