in source\branches\2.0.0.x\Source\DataAccessLayer.WebServiceClient (rev 433 in subversion) around line 645 where the Method that calls the Custom SP from the proxy.
There is an if statement that is checking the return type of the custom SP (collectionClassName, void, or DataSet)
on the line where it calls the procedure that returns void... it omits the (start, pageLength) parameters which make sense to since we aren't returning anything...
HOWEVER,
In ../DataAcessLayer.WebService/WebService.cst where the service is generated, the Custom Procedure does NOT check the return type and OMIT the start and pageLength parameters if it is void.
This results in the WebServiceClient trying to call a WebService Method that doesn't exist (the one with start and pagelength) (and a compile error).
To duplicate this, create a Custom Stored Procedure with no return value or dataset.
PS... i solved this locally by just making the client call the service with the useless parameters. This probably isnt' the right fix, but I'll wait for the update.