Just a gut instinct but do you have any code in your form's constructor besides a call to InitializeComponent? The constructor (ctor) of your form is called by the designer. If your ctor attempts to load anything that is normally not accessible at design time (such as databases) then it'll fail. Anything beyond initialization of UX fields should be postponeded until the OnLoad
method is called.
Click the Show Call Stack
link and look at what is being called.