can i use a generic list in a WCF called from silverlight?

when i return a gen开发者_C百科eric List of my custom object in a wcf service, silverlight gives me this error when i update my service reference (and the reference.cs file is completely blank)

ugly ones like this:

Warning 18  Custom tool warning: Cannot import wsdl:binding
Detail: There was an error importing a wsdl:portType that the wsdl:binding is dependent on.
XPath to wsdl:portType: //wsdl:definitions[@targetNamespace='']/wsdl:portType[@name='Service1']
XPath to Error Source: //wsdl:definitions[@targetNamespace='http://tempuri.org/']/wsdl:binding[@name='CustomBinding_Service1']  C:\Silverlight\POCFinRap\FinRapSilverlightPoc\FinRapSilverlightPoc\Service References\ServiceReference2\Reference.svcmap    1   1   FinRapSilverlightPoc

When i change the return type to a string, all goes fine. (also when i return a List<string> it gives me the errors)

edit 1: by the way: it's SL4 edit 2: i have a silverlight project and a webproject (default created by vs2010) and the SVC is in the webproject.

After a LOT of trial and error and a post which i clicked away accidentily so i can't give him/her credits:

The 'reuse types in referenced assemblies' checkbox gave me the troubles.