If QueueMetrics crashes with an exception like:
[ERR] -- Inner Exception --
Exception: java.nio.BufferOverflowException
Stack trace:
java.nio.BufferOverflowException
at java.nio.charset.CoderResult.throwException(CoderResult.java:259)
at java.lang.StringCoding$CharsetSE.encode(StringCoding.java:344)
at java.lang.StringCoding.encode(StringCoding.java:378)
at java.lang.String.getBytes(String.java:812)
at java.io.UnixFileSystem.getBooleanAttributes0(Native Method)
at java.io.UnixFileSystem.getBooleanAttributes(UnixFileSystem.java:228)

this means that it is trying to read a file using the current Locale that is set for your server but this is not correct for QueueMetrics. You can check what is the encoding of the file names in your local server by typing "locale".

You can anyway force it to UTF-8 by changing JAVA_OPTS in the file /etc/init.d/queuemetrics:
JAVA_OPTS="-Xms512M -Xmx512M -Dfile.encoding=UTF-8"
Or, if it still does not work:
JAVA_OPTS="-Xms512M -Xmx512M -Dfile.encoding=ISO-8859-1"
Make sure that you kill the current Java process and restart it before logging on again in QM.

This error might also be triggered when reading a directory that has too many files, e.g. the place where you store audio recordings. You can override this behaviour by using the LocalFilesByDay storage model - it will also be way faster when retrieving recordings. See e.g.: http://astrecipes.net/index.php?n=387 and http://astrecipes.net/index.php?n=388