The 3.15.1 fixes a small bug in .NET release that could
throw unchecked exceptions on inaccessible current working
directory (for example when run as a service process).
The .NET build of Carrot2 could fail with an unchecked exception thrown
from the underlying I/O subsystem if the process's current working directory was
inaccessible. This bugfix works around the problem.
For a complete list of improvements and bug fixes, see JIRA