the bosch dishwashers are known for faulty inlet/water fill valves. that is a very real possible problem, however, have a tech out immediately.
you can try a do it yourself approach with the valve. replace the valve with part number BT-425458. (your local parts depot should have it, or try an online store such as "AP Wagner" or "Sears". My shop carries it at our parts department).
*notice; The new valve should have the solenoid coil laying horizontal, the original likely will be vertical. they have a history of failing in the "open" position, letting water in even with the unit "off" I've seen many insurance claims due to this failure, especially in the late 90's early 2k's. I'm sure there are still thousands out there. I should add, other possibilities could be, one being back flow throuh the drain line (hooked to a garberator?).
*If it is only happening when nothing else is in use, i.e. water running in sink, garb. running, including the dishwasher, I'd bet on the valve.
hope that helps,
good luck
p.s. if you provide a model number you should be able to get a manual via a pdf on the b/s/h home site here,
http://www.bosch-home.com/us