Created attachment 8370 [details]
A minimal testproject, working on windows, throws the described error on mono.
Linq2Sql throws "System.IndexOutOfRangeException: Array index is out of range." when calling FirstOrDefault on a simple DataContext-Table. Count works and returns the number of rows in the table.
I added a test project. Simply exchange the ConnectionString in Program.cs and compile the application.
I'm using mono version 3.10.0 on Archlinux (ARM).