CnTWaLK unexpectedly returns zero

	Hello.

	I've not used CnTWaLK before, and am finding it not working as
	expected.  I'm looking for some clues as to why.

	I'm running RHEL 6.0 and MRTG 2.16.2 (actually RH's "current"
	2.16.2-5 FWIW).  I have a CAPWAP controller managing some 
	lightweight 802.11 access points, and am looking to track
	the count of 802.11 clients the controller knows about.  There
	aren't very many, as the controller is new and still under test.

	From snmpwalk, I can see one client for the last while, since
	before I set up MRTG monitoring.

joe(user)43: snmpwalk capwap 1.3.6.1.4.1.9.9.599.1.3.1.1.6
Did not find 'cldRegulatoryDomain' in module CISCO-LWAPP-DOT11-MIB (/usr/share/snmp/mibs/CISCO-LWAPP-AP-MIB.my)
CISCO-LWAPP-DOT11-CLIENT-MIB::cldcClientProtocol.'P. ...' = INTEGER: dot11n24(6)
joe(user)44: 

	I'ld expect MRTG to give me the same result, using the following
	options and target specification.

Options[_]: gauge,growright,nopercent,noo
Target[capwap-dot11-clients]: CnTWaLK1.3.6.1.4.1.9.9.599.1.3.1.1.6&CnTWaLK1.3.6.1.4.1.9.9.599.1.3.1.1.6:public@capwap

	However, dumping the relevant RRD file shows

<!-- 2013-06-17 12:05:00 IST / 1371467100 --> <row><v> NaN </v><v> NaN </v></row>
<!-- 2013-06-17 12:10:00 IST / 1371467400 --> <row><v> 0.0000000000e+00 </v><v> 0.0000000000e+00 </v></row>
<!-- 2013-06-17 12:15:00 IST / 1371467700 --> <row><v> 0.0000000000e+00 </v><v> 0.0000000000e+00 </v></row>
<!-- 2013-06-17 12:20:00 IST / 1371468000 --> <row><v> 0.0000000000e+00 </v><v> 0.0000000000e+00 </v></row>
<!-- 2013-06-17 12:25:00 IST / 1371468300 --> <row><v> 0.0000000000e+00 </v><v> 0.0000000000e+00 </v></row>
<!-- 2013-06-17 12:30:00 IST / 1371468600 --> <row><v> 0.0000000000e+00 </v><v> 0.0000000000e+00 </v></row>
<!-- 2013-06-17 12:35:00 IST / 1371468900 --> <row><v> 0.0000000000e+00 </v><v> 0.0000000000e+00 </v></row>
<!-- 2013-06-17 12:40:00 IST / 1371469200 --> <row><v> 0.0000000000e+00 </v><v> 0.0000000000e+00 </v></row>
<!-- 2013-06-17 12:45:00 IST / 1371469500 --> <row><v> 0.0000000000e+00 </v><v> 0.0000000000e+00 </v></row>
<!-- 2013-06-17 12:50:00 IST / 1371469800 --> <row><v> 0.0000000000e+00 </v><v> 0.0000000000e+00 </v></row>
<!-- 2013-06-17 12:55:00 IST / 1371470100 --> <row><v> 0.0000000000e+00 </v><v> 0.0000000000e+00 </v></row>
<!-- 2013-06-17 13:00:00 IST / 1371470400 --> <row><v> 0.0000000000e+00 </v><v> 0.0000000000e+00 </v></row>
<!-- 2013-06-17 13:05:00 IST / 1371470700 --> <row><v> 0.0000000000e+00 </v><v> 0.0000000000e+00 </v></row>
<!-- 2013-06-17 13:10:00 IST / 1371471000 --> <row><v> 3.9333333333e-01 </v><v> 3.9333333333e-01 </v></row>
<!-- 2013-06-17 13:15:00 IST / 1371471300 --> <row><v> 1.0000000000e+00 </v><v> 1.0000000000e+00 </v></row>

	as if MRTG hadn't noticed for about an hour.

	Since I took that extract, MRTG is now showing zero again, even though snmpwalk continues
	to show one client.

	Can anyone suggest what I might be missing, other than an upgrade to a really current
	release of MRTG?

	Thanks in anticipation and best regards,
	Niall O'Reilly