See details in http://jira.atlassian.com/browse/GHS-1655
Waiting for a correction of IssueUtilsBean, the solution is to force its refresh when Minyaa plugin is loaded by redeclaring the component in the atlassian-plugin.xml as follow:
<component key="IssueUtilsBeanFix" name="IssueUtilsBeanFix" class="com.atlassian.jira.issue.IssueUtilsBeanFix" > <interface>com.atlassian.jira.issue.IssueUtilsBean</interface> </component>