The psadump utility that is shipped with Plesk 7.1.6, expect the version number of the MySQL server to always be in the format x.x.x, where x is a digit. We have however had cases where the MySQL version was x.x.xX, where x is a digit and X is a letter. Below is a hack on the regex to make psadump work properly again.
In the {PSA_BASE_DIRECTORY}/lib/perl5/BU/PSA/Const.pm file, change:
$mysql_version_str =~ m/[Vv][Ee][Rr]\s+[0-9\.]+\s+Distrib\s+([0-9\.]+)[\s,]/;
to:
$mysql_version_str =~ m/[Vv][Ee][Rr]\s+[0-9\.]+\s+Distrib\s+([0-9\.\w]+)[\s,]/;
UPDATE:
This problem has been resolved in Plesk for Linux version 7.1.7.