I ride a Jumbo Cannondale Quick - SL1 model. I do not ride in winter - so bike has had perhaps 16 months usage (and now covered some 5,500km). I over 6foot, but not particularly heavy - perhaps all-up weight of bike, me + items on bike while riding total some 225lbs. I have used 32mm (and lately 35mm) tires - inflated so there is a little 'give' in the tire (well below 100).

Front wheel has performed flawlessly - rear wheel suffered three broken spokes, after which time I lost all confidence in the wheel (especially as I was preparing for my first century). Based on work I did on one spoke repair when LBS was closed, I think part of problem was that the spoke tension had never been properly done.

So the 3rd broken spoke was some 6 months outside the warranty period (but because of winter hibernation it was only about 12 months and 3,00km usage). After some discussion with LBS (and LBS/Cannondale) I was offered a free Shimano rear wheel (RS11) - albeit in the end I opted for a discounted upgrade to a Shimano RS31 rear wheel (despite reduced spoke count, this has performed flawlessly so far).

I have just ridden my bike back from it final free service (where I paid for a new chain and rear cable) - bike still puts a smile on my face when I ride it. Hope you soon get your bike back to such a wonderful state.

Based on my limited experience:
(a) Consider requesting help from LBS/Cannondale (depending on how long ago you purchased bike, and specifics of your usage);
(b) whichever rear wheel you get (and intuitively more spokes should result in a more durable wheel), make sure the spokes are properly tensioned before using the wheel.