DB Error: MySQL server has gone away

Stack Trace:

File: /var/www/html/classes/paper/PaperCommentDAO.inc.php line 106
Function: DAO->retrieveLimit("SELECT a.* FROM paper_comments a WHERE paper_id = ? AND comment_...", Array(3), 1)

File: /var/www/html/classes/submission/reviewAssignment/ReviewAssignmentDAO.inc.php line 421
Function: PaperCommentDAO->getMostRecentPaperComment("3789", 1, "5083")

File: /var/www/html/classes/submission/reviewAssignment/ReviewAssignmentDAO.inc.php line 123
Function: ReviewAssignmentDAO->_returnReviewAssignmentFromRow(Array(25))

File: /var/www/html/classes/tasks/ReviewReminder.inc.php line 116
Function: ReviewAssignmentDAO->getIncompleteReviewAssignments()

File: /var/www/html/plugins/generic/acron/AcronPlugin.inc.php line 98
Function: ReviewReminder->execute()

File: (unknown) line (unknown)
Function: AcronPlugin->callback("LoadHandler", Array(3))

File: /var/www/html/lib/pkp/classes/plugins/HookRegistry.inc.php line 79
Function: call_user_func(Array(2), "LoadHandler", Array(3))

File: /var/www/html/lib/pkp/classes/core/PKPPageRouter.inc.php line 143
Function: HookRegistry->call("LoadHandler", Array(3))

File: /var/www/html/lib/pkp/classes/core/Dispatcher.inc.php line 130
Function: PKPPageRouter->route(Object(Request))

File: /var/www/html/lib/pkp/classes/core/PKPApplication.inc.php line 170
Function: Dispatcher->dispatch(Object(Request))

File: /var/www/html/index.php line 65
Function: PKPApplication->execute()

DB Error: MySQL server has gone away

Stack Trace:

File: /var/www/html/lib/pkp/classes/session/SessionDAO.inc.php line 103
Function: DAO->update("UPDATE sessions SET user_id = ?, ip_address = ?, ...", Array(8))

File: /var/www/html/lib/pkp/classes/session/SessionManager.inc.php line 177
Function: SessionDAO->updateObject(Object(Session))

File: (unknown) line (unknown)
Function: SessionManager->write("g2pnk9s6lcsbthf6m1t1n942k4", "")

File: (unknown) line (unknown)
Function: session_write_close()