Thanks Nofew.
I have been trying to follow the comings and goings of the display pics and have noticed that where the other person signs on makes a difference.
If the person logs on and off from a desktop computer the dp is saved on my msn but if they sign on and off from their mobile, dp disappears.
So if I am chatting with them, dp shown, they sign off from desktop, dp stays for days on end but if they are on mobile the moment they sign off, dp disappears and does not reappear until they sign back on.
The display pic is always the same and it doesn't matter if I start a conversation or not.
So yes, not a function of being blocked but how/where msn stores the dp but it is weird that this never happened in last version....
So for many of the disappearing dp, the person tends to use mobile so that explains why pic is there during work hours and odds are I am blocked (not something personal as they are working and using the msn for work so personal contacts would be blocked until they had free time)