Hello, Marco,
Something you're doing is crashing Julia. This is bad, but without more information, it's impossible to tell what's going on or where the problem is--it could be a bug in Julia, ZMQ.jl, IJulia.jl (maybe), or somewhere else entirely.
Can you post the code you're trying to run (or preferably, a short snippet that causes the problem, along with the output of versioninfo()?
You also might look through closed IJulia.jl issues.
Cheers,
Kevin