I think I'm having the same problem here.
Code:
[echo] [simulate] You may now run Gazebo and your DriverStation
[echo] [simulate] Running Code.
[java] resources = |sun.misc.CompoundEnumeration@2401f4c3|
[java] platform: /Linux/amd64/
[java] Initialized simulator/dio/1/2
[java] Initialized simulator/dio/3/4
[java] NOTE|WPILibJSim: Encoder.setDistancePerPulse() assumes 360 pulses per revolution in simulation.
[java] NOTE|WPILibJSim: Encoder.setDistancePerPulse() assumes 360 pulses per revolution in simulation.
[java] NOTE|WPILibJSim: Encoder.setDistancePerPulse() assumes 360 pulses per revolution in simulation.
[java] NOTE|WPILibJSim: Encoder.setDistancePerPulse() assumes 360 pulses per revolution in simulation.
[java] WARNING|Gazebo Transport: Ignoring unsubscribe: topic: "/gazebo/frc/simulator/pwm/7"
[java] host: "192.168.1.8"
[java] port: 52438
[java] msg_type: "gazebo.msgs.Float64"
[java] java.lang.NoClassDefFoundError: edu/wpi/first/wpilibj/command/TimedCommand
[java] at java.lang.ClassLoader.defineClass1(Native Method)
[java] at java.lang.ClassLoader.defineClass(ClassLoader.java:763)
[java] at java.security.SecureClassLoader.defineClass(SecureClassLoader.java:142)
[java] at java.net.URLClassLoader.defineClass(URLClassLoader.java:467)
[java] at java.net.URLClassLoader.access$100(URLClassLoader.java:73)
[java] at java.net.URLClassLoader$1.run(URLClassLoader.java:368)
[java] at java.net.URLClassLoader$1.run(URLClassLoader.java:362)
[java] at java.security.AccessController.doPrivileged(Native Method)
[java] at java.net.URLClassLoader.findClass(URLClassLoader.java:361)
[java] at java.lang.ClassLoader.loadClass(ClassLoader.java:424)
[java] at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:331)
[java] at java.lang.ClassLoader.loadClass(ClassLoader.java:357)
[java] at org.usfirst.frc.team2832.robot.Robot.robotInit(Robot.java:42)
[java] at edu.wpi.first.wpilibj.IterativeRobot.startCompetition(IterativeRobot.java:65)
[java] at edu.wpi.first.wpilibj.RobotBase.main(RobotBase.java:198)
[java] Caused by: java.lang.ClassNotFoundException: edu.wpi.first.wpilibj.command.TimedCommand
[java] at java.net.URLClassLoader.findClass(URLClassLoader.java:381)
[java] at java.lang.ClassLoader.loadClass(ClassLoader.java:424)
[java] at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:331)
[java] at java.lang.ClassLoader.loadClass(ClassLoader.java:357)
[java] ... 15 more
[java] WARNING: Robots don't quit!
[java] ---> The startCompetition() method (or methods called by it) should have handled the exception above.