The thread on poor little Fern is a good place to start. Pancreatitis is a really vicious condition and one which Jack, our 9 year old Toffee Roan, has had on several occasions. Its caused by there being too much fat in the dogs system which the Pancreas can't deal with. If I remember rightly, its something to do with the over-production of enzymes (whereby the overload actually causes the enzymes to digest the pancreas and other bits and pieces - someone will, I'm sure, clarify on my behalf!). The symptoms are very unpleasant - vomitting, diarrohea, listlessness, very tender and swollen tummy and a great deal of discomfort all round. Poor Jack could hardly move for the pain and would stand motionless for ages as a result or slowly wander around the house as if searching for relief. As I mentioned before, he has had it on numerous occasions and can strike very, very quickly - often in a matter of minutes. One moment he's fine, the next he's suffering. Fortunately, we know what to look for so at the first sign of trouble he's off to the vet for anti-inflamatories, anti-biotics, painkillers etc. The trick is NOT to give him any fatty scraps, sweets, chocolate etc (easier said than done when the dog is a walking dustbin!!) so as to minimise the risk of him contracting it again. Hopefully you're little one will be back on his paws again soon!
