I am still getting compiler warnings when I recompile business objects.I have tried cleaning the solution, cleaning the project , and deleting the .dll but the warnings are still appearing. I can still run the app but the warnings (over 1000) are abit of a nuisance...what can be done to remove them (Screen shot attached)

There is more than a single version of this assembly on your development machine. If you have the BO in the GAC, you can see things like this at design-time.