The message is pretty much as above but here it is in full:
"Runtime error! Program C:\... R6025-pure virtual function call." I have not truncated "C:\..." that is exactly how it is in the message. I have assumed it is the Photoshop executable.
With regard to my plug-ins, no I have not disabled them. I will do so and see what happens.
It may be a day or so before I have anything because as I said before this problem is intermittent and can go a couple days before the problem reoccurs.
Thanks