Looks like there is a load issue when using DLLs from both .net 4.0 and the SIS OSIsoft adapters. You get a runtime error.
The solution is to add the folloing to your app.config file:
Not sure all the details of why, but there is a pretty good explanation here: http://msdn.microsoft.com/en-us/library/bbx34a2h.aspx
Hope OSIsoft solves this issue soon, so we do not need this workaround, as it may interfare with other things.