Hi, I faced a similar issue today on a debian server. We had some nework problems yesterday. Master was not able to communicate with the slaves. After the network establishment the jobs where still stuck.
I tried to reeboot server & slaves but still faced the same issue. When you stop jenkins a queue.xml is created and restored a next boot. I could solve my problem by stoping jenkins, deleting the queue.xml and start jenkins again. BR, Bertrand.
