NetBSD is strict:
GLib (gthread-posix.c): Unexpected error from C library during 'pthread_mutex_unlock': Operation not permitted. Aborting.
I think isomething tries to unlock already unlocked mutexes.
#0 0x00007f7ff61db90a in _lwp_kill () from /usr/lib/libc.so.12
#1 0x00007f7ff61db1e2 in abort () from /usr/lib/libc.so.12
#2 0x00007f7ff6b85d70 in g_thread_yield () from /usr/pkg/lib/libglib-2.0.so.0
#3 0x00007f7ff7a3f94a in gtk_main () from /usr/pkg/lib/libgtk-x11-2.0.so.0
#4 0x00000000004191bd in main ()
$ env PTHREAD_DIAGASSERT=ae lxpanel
lxpanel: can't load cpu plugin
lxpanel: Error detected by libpthread: Unlocking unlocked mutex.
Detected by file "/usr/src/lib/libpthread/pthread_mutex.c", line 423, function "pthread__mutex_unlock_slow".
So I patched glib2 to not abort on this so I can still use lxpanel.
Older glib2 doesn't abort.
I am not sure where the problem is... maybe somewhere in lxpanel there is a mutex gettig unlocked twice I think.