Assuming its a smaller Cargo - 0811, 0813 etc (air over hydraulic), check your brake master cylinders and reservoirs - on the chassis side rail (outside). Make sure there is brake fluid in both reservoirs. Could be there is a leak and if so there may be no fluid in one of these reservoirs. Depening on whether its an L or V split, you may have full brakes on rear but only one on the front.
Needs to be checked out. Should not be driven until its resolved.
JD
March 2009