We have recently seen MonetDB become unresponsive several times. Upon restarting, after mserver has been sent the TERM signal, merovingian.log contains lots of "unknown state: 4" entries, repeated many times without linefeeds. 

We're running Jan2014-SP2 (official binaries) on Ubuntu server 14.04. We had the same database running on Jan2014-SP1 on Ubuntu 12.10 for several months without this issue.

I have submitted as a bug (https://www.monetdb.org/bugzilla/show_bug.cgi?id=3499).

Thanks,

Pete.