Hi Brian1042
Paid upgrade you mean using miles? If that is the case then there is a 'dance' that goes on in the 24 hours or so before flight time in which you may see flights and booking classes waitlisted and upgrades declined.
This is spelled out in this excellent thread from the Australian Frequent Flyer forum:
http://www.frequentflyer.com.au/comm...des-13864.html
Regards
lme ff