Dan,
Which version of LabVIEW do you have?
As per the KnowledgeBase bellow, in versions of LabVIEW prior to 5.1 you would get errors accessing the ambient properties.
ActiveX Controls in LabVIEW 5.0.1 Containers Cannot Access Ambient PropertyDo your controls use the Ambient.UserMode to determine when the control is being used in a development environment? When embedding ActiveX controls into a container on the front panel, by default, the ActiveX control generates and responds to events, i.e. it is running, even when LabVIEW is in edit mode.
Right-click an ActiveX container and select Advanced»Design Mode from the shortcut menu to display the container
in design mode while you edit the VI. In design mode, events are not generated and event procedures do not run. The default mode is run mode, where you interact with the object as a user would.
Information can be found in the LabVIEW help files
Zvezdana S.