My character acquired nemesis staff, ghost axe, AND black wand veteran reward without 54 months.
Freedom removed the veteran rewards program and introduced the paragon rewards program. How many tokens do you have? What does your rewards tree look like? The attack power options are:
Tier 3: Sands of Mu/Ghost Slaying Axe
Tier 5: Nemesis Staff/Blackwand
Tier 6: [choice of what you didn't pick in Tier3/5]
http://paragonwiki.com/wiki/Paragon_Rewards_Program
Paragon Wiki: http://www.paragonwiki.com
City Info Terminal: http://cit.cohtitan.com
Mids Hero Designer: http://www.cohplanner.com
Interesting. I've had the window bug out and prompt me a second time before, but trying to actually take a second power didn't work (I had to do 'choose nothing' to make the window go away).
So it could be a similar bug, but it also might be that you really do have it now with the new rewards system.
It's the tiers. I recently finished tier 6.
I picked the axe and staff as I normally do, but then it asked me if I wanted the staff or wand again and I couldn't leave the screen without picking the wand cause I already had the staff. As far as I'm aware I shouldn't be able to have both on one character, unless it's been 54 months apparently. Which it hasn't. I've only got the 3 year badge.