RS is marking a valid LINQ query as having an error in it:
Dim newList = From foo In fooList _
Group foo.Value1, foo.Value2 By key = foo.Value1 Into Group _
Select key, Group
The second and third Group keywords are both marked as errors by RS. I don't know if this is an error specific to VB, or if it's in the C# version as well (I don't have a RS C# license, so don't have an easy way to test it).
I searched for this in the forums and couldn't find anything. My apologies if it's already been mentioned.