This bug has been reported a couple of times. The first time it was here:
https://sourceforge.net/p/robocode/discussion/116459/thread/141935ac
java.lang.InternalError: internal error: SeedGenerator thread creation error.
at sun.security.provider.SeedGenerator$ThreadedSeedGenerator.run(Unknown Source)
at java.lang.Thread.run(Unknown Source)
Caused by: java.security.AccessControlException: Preventing SeedGenerator Thread from access to SeedGenerator ThreadGroup
at net.sf.robocode.host.security.RobocodeSecurityManager.checkAccess(RobocodeSecurityManager.java:114)
at java.lang.ThreadGroup.checkAccess(Unknown Source)
at java.lang.Thread.init(Unknown Source)
at java.lang.Thread.init(Unknown Source)
at java.lang.Thread.<init>(Unknown Source)
... 2 more
I can bypass the issue if I turn off the security manager via the DNOSECURITY flag but I don't really want to do this.
Fixed with version 1.9.2.6