Check your glow plugs with a Multimeter (search for the thread here or go the dieselgaint site if you do not know how to check them).

If you cannot tell where your injector is leaking (or if it is the fuel return hose) spray it off with brake cleaner and clean all of the crap that is on or around the injector.
Get a flashlight with a strong lignt and start the car and find out where the leak is.

I do not know how cold weather effects biodiesel however; when your close to empty put in several gallons of regular diesel fuel and see if you have the same symptoms.
If your symptoms go away it is the fuel that you are using.

__________________
84 300D, 82 Volvo 244Gl Diesel