Render nodes not contributing

[mgibeault]

Any development on this problem I had a while back?
I get it from time to time. No idea what's causing it and how to get them back online.
Here's the relevant text in the progress window:

...
Starting DR 0
dr host: 10.88.196.103:20211
dr host: 10.88.197.6:20211
dr host: 10.88.198.192:20211
dr host: 10.88.195.194:20211
dr host: 10.88.196.135:20211
dr host: 10.88.198.205:20211
Host 10.88.196.103:20211 added to waiting list
Host 10.88.197.6:20211 added to waiting list
Host 10.88.198.192:20211 added to waiting list
Host 10.88.195.194:20211 added to waiting list
Host 10.88.196.135:20211 added to waiting list
Host 10.88.198.205:20211 added to waiting list
Could not use any of the selected (6) hosts for distributed rendering!
Preparing camera sampler.
...

[palosanto]

Sometimes it happens to me. Restart the license server and also re-start the spawners in the rendering nodes. They should then resume rendering after a short while.