I had a 748 which had a rusty frame, so the thread my have been mine originally. The bike was 6 months old and started getting glassic spiders web type markings abd bubbles on the frame. Most upsetting. I suspect it was down to a mozzarella splatter just prior to frame painting.
Anyway, Ducati UK, bless their little cam lobes, replaced it without question. Infact the bike had a few small problems with an oil leak bewteen case and rear barrel and they changed that too with not so much as a sharp intake of breath. Rear shock went just prior to going out of warranty - replaced.... So, IMO, they're very good and you should contact them to sort it out.
Hope that helps,