The LINQ implementation in 1.4 has only been tested from C#. It is likely that the expression trees generated when using LINQ in VB.NET will in some cases be slightly different and that we will need to account for that.

We are not planning to hold up the 1.4 release for this, but will likely come out with a 1.4.1 release if necessary to support LINQ in VB.NET as well as C#.