Where are widget screen positions (coordinates) stored?
Dashboard widget positions are stored in /Users/USERNAME/Library/Preferences/com.apple.dashboard.plist (where USERNAME is your username on your Mac) and can be accessed by using Xcode to edit or possibly even TextEdit. When you open the file, you're looking for the values under 'layer-gadgets' and then 'Item X' (where X is the widget's position number in the Dashboard layout). Just locate and change 'pos-x' and 'pos-y' for your widget.

Good luck!