I am working with an integration against a SalesForce solution, where there is a very complex structure in SalesForce, where there are references that will never end in a recursive situation. This gives you an out of memory exception or your Visual Studio crashes. 

The solution is to open the BizTalk map with an XML editor and change the (GenerateDefaultFixedNodes=”Yes”) to (GenerateDefaultFixedNodes=”No”) or (GenerateDefaultFixedNodes=”RequiredDefaults”). If you have defaults in your map then you would need to take the last “RequiredDefaults” as you otherwise will miss those in your output.
Remember to test your mappings after you have done this change. See here for more information: http://msdn.microsoft.com/en-us/library/aa561485.aspx