You need to give more information. What was your previous firmware level? Have you tried rebooting the router (via the GUI)? Have you tried an electrical reset (unplug the power cord from the router and the AC wall outlet (while leaving the router's power button 'on'), and wait a few minutes before plugging everything back in)?
Are you using ports 5-8 on your router? The electrical reset above may help (temporarily). But if it doesn't, consider getting a $30 switch and not using those ports for a more stable network environment.
Finally, when was the last time you did a full reset after flashing the firmware you want to use, and not using a saved backup config file, nor plugging in any USB device that you were using to run scripts from?