Hi Marco,
There's a couple of settings that may help:
1. Open Input Director on your Director system
2. Switch to the "Director Preferences" tab
3. Scroll all the way down to the Advanced Settings
4. Change the "Check offline systems availability every" to, e.g. 10 seconds
5. Also, perhaps set the option "Hotkey to rescan and update systems available" (e.g. to alt-win-R).
Let me know if that doesn't help.
Regs,
Shane.