There's very likely a little unrest inside Palm's corporate walls today on news that the company's falling a little short of its financial expectations, so CEO Jon Rubinstein has wasted no time firing off an all-employee letter explaining the sitch while trying to calm some nerves in the process. As analysts had feared, Rubinstein clearly isn't pleased with the way the company's launch on Verizon has gone -- but he's already got a plan in place involving some 200 "Brand Ambassadors" deployed to Verizon stores to help get reps the straight dope on Palm products and a refreshed ad campaign across several mediums. Is it enough? That remains to be