I don't think you should worry about the rest of your quiver. It's very unusual for a North sail to fail in the manner you have described for no reason.
I have only ever owned North and have never had a crease that split or tear open. Yes i've had the odd crease appear from time to time (always my fault or through abuse by airport staff), but never had one fail. We all know that creases can be anything from almost invisible lines to hard, brittle, white sharp folds!
I currently own 4.5 and 5.0 07 ICE , 5.4 07 DUKE, 6.0 07 X-TYPE, 9.9 08 F-RAM, 6.8 and 7.8 08 WARPS, 9.0 and 11.0 07 WARPS, and am picking up my new 10.0 08 WARP today. I have no problems resulting from creasing in any of these.
My smaller wave sails have seen some abuse over the last 12 months and are still holding together well. (countless wipeouts straight into the main panel have not resulted in any splits or tears yet,,,,,,fingers crossed. Yet there are many of the normal stress lines and wrinkles)
My X-TYPE has been used over 40 times and has done some traveling as have my race sails. (in and out of planes, trains and automobiles. Southern hemisphere to northern and back again, as well as countless road trips) In my experience creasing tends to happen during travel and transportation as well as rigging. (seeing my sailbag at the airport with 20 or 30 pieces of luggage piled on top is a horrible experience)
My old 05 R-TYPE had a small crease in an upper panel when i bought it,(a faint fold line of about 3 inches in length) nothing too serious. I kept a close eye on it over the 8 months that i sailed it, and noticed that it worsened over time despite my efforts to take care when rigging and de-rigging.
My conclusion at the time was that a crease is effectively the weakest point of any panel (It's like thick paper. If you fold it repeatedly in the same place, it will eventually tear without too much effort).
If any excess pressure while rolled or while rigging is received by the panel, the most likely place to degenerate further will be the weakest point,,,, the crease. (like re-folding the paper again)
I also love the white double layer monofilm used by north. The clear monofilm used in the main panels feels a little thicker than some other brands that my friends sail. Particularly with the race sails! Yet this extra thickness does not result in a more brittle panel. They have managed to find the right balance between flexibility (bending ability) and elasticity (stretching ability).
I have no wise conclusion on this subject other than the obvious,,,,, "no sail will last forever". And no manufacturer will ever have a perfect record with failures. I can say however that in my opinion north monofilm is as robust and longlasting as anything on the market today.
I agree with the other poster who suggested you take the sail back to the shop where you bought it from. You never know, they might at very least repair it for you.
Good Luck Matt, and enjoy the rest of your quiver.