Tom,
I am sending only 1 line of data, there is another example below where I send 3 lines of data and use two. The MSG var was a sloppy leftover from snagging an example script, probably slabinfo - disregard it.
When changing a graph stanza in hobbitgraph.cfg I normally kill the old rrd file. There are ways to parse those rrd files to see what info is in there (look at rrdtool dump options). Might be a good idea to see if you are even getting the data or if you are getting NAN. NA2CPU : ${NA2CPU} note the quoting
By the way, what do you have in: /home/xymon/client/etc/clientlaunch.cfg?
I'm sure that others on the list who are more familiar with this can assist if you are not able to sort it out with my scattered bits of info....
Here is another example where data is sent and graphed: