LLBLGen Pro Team
The Hague, The Netherlands
that's due to a breaking change with the 'Expression' class I think with linq, but as you don't give any stack trace I have to guess. Other than that it should be fine.
However as 2.6 was released in 2008, it might run into difficulties when MS decides to change something in .NET. In that case you have no other choice but to either upgrade to our latest version or compile the runtime sourcecode yourself (the sourcecode is available on disk in the install and also on the website under 'my account -> 2.6'.
We don't fix issues in v2.6 anymore.