Finally tracked down a really perplexing problem I've been having with some windows slaves. It appears that somehow - the slaves are getting "stuck" with a particular set of environment variables. No amount of reconfiguration of the windows box - switching user it runs as, running interactively, etc. would change it.
The only thing I found that cleared it up is completely deleting the slave from jenkins node list, and re-adding it - then it finally reset what environment variables would be present on the slave. Note - I didn't do ANYTHING other than changing the 'secret' value on the windows box. i.e. I did not reinstall service, relaunch from the nodes list, etc. - just changed the secret that it used to connect with.
Is this something obvious that I'm missing in how windows slaves are supposed to behave?
Slave is being launched with java web start.