Pi 2 with emonhub stops posting to emoncmc.org

I have  set up a Pi 2 model B V1.1 and a RFM12B with the latest emonhub software posting to my emoncms.org account just to keep up to date with developments. I have to report that every now and then it stops posting. I can still SSH into the Pi so that is still running. I reboot and it works OK for a time and then stops posting.

emonhub -dl shows:-

2015-03-06 23:06:59,122 DEBUG 2873 Append to 'emonCMS' buffer => time: 1425683219.09, data: [17, 1818, 2895, -66], ref: 2873
2015-03-06 23:06:59,224 INFO emonCMS sending: http://emoncms.org/input/bulk.json?apikey=E-M-O-N-C-M-S-A-P-I-K-E-Y&data=[[1425683219.09,17,1818,2895,-66]]&sentat=1425683219
2015-03-06 23:06:59,340 DEBUG emonCMS acknowledged receipt with 'ok' fromhttp://emoncms.org

Are there any other logs or procedures that would help in identifying where the problem is. The RFM12B is fitted with an RFM69CW 433Mhz if that might make a difference.

Regards

Ian