Somehow I do always get this bug while trying to start Windows slaves from a Linux jenkins instance via SSH. SSH is configured properly on the machine and jenkins is configured to start a session using the Administrator account, which works fine.
The log is available at https://gist.github.com/ssbarnea/370949586b622f751d07 and the important part being:
' on tocco
[marvin] $ /bin/bash C:\Users\Administrator\hudson5000371039477233927.sh
hudson.util.IOException2: Slave JVM has not reported exit code. Is it still running?
Caused by: java.io.IOException: Cannot run program "/bin/bash" (in directory "C:\tools\cygwin\home\Administrator\marvin\marvin"): CreateProcess error=3, The system cannot find the path specified
at java.lang.ProcessBuilder.start(Unknown Source)
The windows path is correct, being created by Jenkins, but it seems that he execution of /bin/bash is the one that fails. If one does manually performs ssh to the machine, using the same credentials, they would be able to run /bin/bash.
I believe that the problem is because Jenkins is assuming that being a Windows machine it has to provide a Windows path to the CreateProcess which probably expects a Unix path instead because the entire shell is run under cygwin.
Still, I tried any combinations of configuring the slave path on the node configuration but none seems to work.