UnityVS 1.8 possible bug with XML.Linq

As i understand System.Xml.Linq is included in Unity 4.2.1f4 and i have no error on compile. BUT! When i open solution in MonoDevelop or UnityVS(Visual Studio 2012) there is NO Xml.Linq in References. Why?
P.S.
Of course when i add this reference manually all works fine but when project file is overwritten all i loose changes to solution, that makes me sad :frowning:

Good news, this bug will be fixed in UnityVS 1.8.1!

Please contact the UnityVS support if you want an interim build with the fix.