Whipping-cream will not stay hard or keep its peaks and gets runny
The brands that used to work may have changed their formulation in response to carageenan shortages. If they use less emulsifier, a lower quality product, or different emulsifiers such as guar gum, locust bean, or xanthan gum, the stability of the whipped cream may suffer.
If the cream you can get isn't stable enough, you can add unflavored gelatin to stabilize it.
Method is in 'Joy of Cooking', or here. 

May2013: Looks like carrageenan is still on the USDA organic list Shortage has eased, but whipping problems could still be due to variations in quality of supply.