I'm having the same issue. Here is my log:
YlandsLog {}
[IN] Ylands Version: 0.6.1.41937
[IN] command line arguments: C:\Program Files (x86)\Steam\steamapps\common\Ylands\Ylands.exe
[IN] Logging On
[EX]U InvalidProgramException: Missing or incorrect header for method InternalTransformFinalBlock
+t System.Convert.ToBase64String (System.Byte[] inArray, Int32 offset, Int32 length)
System.Convert.ToBase64String...