MyQul
Chairman of the Bored
You may have got a wild yeast infection in it. Fruit like raspberries will often have a bloom of wild yeast on their surface which is not noticeable. I have wondered about how to get around this, maybe steeping in vodka before adding as just rinsing in water probably won't do it. Or use tinned raspberries as these will have been pasteurised during the canning process. Real shame though as it sounds like a lovely idea for a summer beer. I too use the GH book quite a lot even if it's just to give me ideas for the type of beer I want to brew next.
Wouldn't blanching the raspberries work. The quick dunk in boiling water should kill the wild yeast but not effect the raspberries too much