Shockwave’s Blog

I’ve recently decided on a bit of a change and bought a Mac. A 13″ Mac Book Pro to be exact. It’s been a bit of a learning experience which has been quite nice after using Microsoft Windows since 3.1.

Anyway, after a few months I started experiencing issues with my Trackpad, the physical click was only working intermittently. I took the laptop into my local Apple store after making an appointment with a ‘Genius’. Unfortunately this was the week of the iPad release meanining I had to avoid the high fives on the walk in. Cutting a long story short, the ‘genius’ replaced the Trackpad… Sorted.

When I got the laptop home, I realised I couldn’t obtain a DHCP address from my router (wired or wireless ruling out a hardware issue in my mind). Following some troubleshooting I found that I could obtain an address when the firewall was disabled. Given that I didn’t want to disable the firewall every time I wanted to lease an IP address, I did a little more research. It appears when the ‘genius’ had replaced the Trackpad, the system clock had been reset to 01 Jan 2000 which caused an issue with the digital signing of certain binaries (krb5dc and nmbd in my instance).

To resolve the issue, I simply restored these files from a Time Machine backup I had taken before I let an Apple ‘genius’ loose with my laptop.

If you’re not lucky enough to have a backup of these system files, my advice would be to add them to your firewall exclusions through System Preferences –> Security –> Firewall –> Advanced – Navigate to the /usr/sbin/krb5dc and /usr/sbin/nmbd then select  ‘allow incoming connections’. You may also need to repeat this for /usr/sbin/mDNSresponder. As always, don’t forget to restart your device to ensure it works.

If you’re experiencing similar issues, give it a go. I am by no means a Mac expert having used one for a few months, but it was simple enough.