Vnc, ssh ports intermittently not accepting connections since upgrading to 10.10.1

Question

Since upgrading I cannot remote access my mac book air 2014. Prior to the upgrade I did not have any issues. I have not changed any networking / firewall settings.
Sometimes it works, other times the vnc and ssh ports do not accept connections.
Running nmap on another host on the local LAN reports all ports as being filtered.
Other times, nmap shows 22, 5900, and the AFP port open, as expected.
I know there have been reports of wi-fi issues, and this machine is using wi-fi.
Is it possible that when the screen blanks after a period of the machine not being used, that the wi-fi connection is going into a power down mode?
I don't see the ports being filtered when I am using the machine, it's only after I've left the house and I try to remotely connect.

Answer 1

On looking at the secure.log on the iMac with OSX10.6.8, I see these entries at each attempt to scp into the iMac:
Dec 29 11:06:20 molika sshd[7248]: in pam_sm_authenticate(): Failed to determine Kerberos principal name.
Dec 29 11:06:26 molika sshd[7246]: Accepted keyboard-interactive/pam for prowat from 137.110.243.132 port 35571 ssh2
Dec 29 11:06:26 molika com.apple.SecurityServer[26]: Session 0x236a14 created
Dec 29 11:06:26 molika com.apple.SecurityServer[26]: Session 0x236a14 attributes 0x20
Dec 29 11:06:27 molika com.apple.SecurityServer[26]: Session 0x236a14 dead
Dec 29 11:06:27 molika com.apple.SecurityServer[26]: Killing auth hosts
Dec 29 11:06:27 molika com.apple.SecurityServer[26]: Session 0x236a14 destroyed
I don't know what to make of this.
Peter R