Bit of a problem with the use of graphical views in Mango that has come up recently.
I have some basic on-off switches in Mango that turn a fan and compressor on and off AND others that are able to vary the fan and compressor speed from 0 to 100%.
When I go to use these switches in the graphical view, I get a "server error has occurred" message and it doesn't work. HOWEVER, when I do this in the data points section...it works just fine.
Well, from the information you've provided i'd say a server error has occurred. Maybe you can check the server console and see if there's any more information about the nature of error.