Hi,
I'm only seeing some references to certain categories as 21-day for Auction style at the ca site. Looks like it's the Motors site that has the 21 day. I did see someone complain in the Community Forums about a 21 day limitation on DVD suddenly showing on Turbolister.
The standard help page at the main site has the normal.
http://pages.ebay.ca/help/sell/duration.html
What are you listing?
If anything, I'm guessing it's a BUG at EBAY.
Danno