There is a documented issue in Visual Basic, where a right click menu will fail to display in a window that was loaded from a right click menu.
Microsoft Article: http://support.microsoft.com/kb/167839

Symptoms:

If you open a window in Hach WIMS using a right click menu item, the right-click menu in the new window will not display.

Work Around / Solution:

The only way to get to the right click menu in the new window is to open it using other means.  For example, most windows in Hach WIMS can be loaded/opened using the drop down menus at the top of the window you are using or shortcut buttons at the top of the window.