Cooking milkbased soups in a CrockPot without curdling

I described below (Lunch: Five dollars, etc.) how I made potato soup in the crock pot. I didn't start it in the crock pot, I started it on the stove, and once I had made the roux and added-heated the milk, I dumped it into the crock pot along wthe potatoes. Covered it and put it on low for two hours, maybe a bit less. The soup had formed a little buttery-looking skin on top by the time I got back, but it didn't look awful. I stirred it up, and it was fine; it had thickened a bit during the two hours (it thickened like crazy once the soup cooled...we had to thin it with a lot of milk to reheat the leftovers) . This was the only time I've tried making a milk-based soup in the crock pot.

Maybe it was the several hours thing that didn't work for your friend? Did she have it on low or high? Not sure what went wrong? If it was me, I'd check out a recipe site like allrecipes.com, and search for soup recipes w milk in a crock pot or slow cooker. See what their technique is, and check the user reviews for tips-tricks-tweaks. Hope her next attempt is more successful...what a bummer to come back from a hike all hungry for soup, and find a curdled mess!

Chris