This problem was odd in that the user was having password prompts being continuously displayed. As described in previous articles – switching the user from cached mode (which was set during automatic configuration) to normal online mode would have dealt with this. However the local administrator told me that the performance of Outlook had dropped dramtically when he did this so he switched back to cached mode. We carried out the change again to see the symptoms and specifically tasks shown in the task list on the right hand side of the screen appeared to not be updating and were very slowly refreshing the screen. Outlook was sluggish to the point of unuseability. So we removed and recreated the mail profile manually and restarted outlook to find the performance was back to what it had been in cached mode but operating without prompts.
So if you experience the same problem – try removing the profile or creating a new manual one and set all the options yourself