It could be that the Nagevis are getting a little long in the tooth. What can happen is that the material in the soles can get a little hard over time, and of course the little knobs on the sole lose some of their bite as they wear down. Both of those things can lead to a loss of traction.
Garmont Sitka XCR Hiking Boot

The current Nagevis are a low-cut trail-running type shoe. They聮re still available for $90 at REI (rei.com) and other places. But, it sounds as if what you have is a little taller, heavier shoe, so maybe the Nagevis have morphed a bit. And it聮s true, today聮s low-cut trail shoes聴and mid-weight boots聴have benefitted in recent years from running-shoe technology.
In any event, for the type of hiking you do, I strongly recommend a mid-height or taller boot. You can still go light but with a bit more foot and ankle protection than a low-top shoe. Garmont makes a great shoe called the Sitka XCR ($160; garmont.com). It combines the height and durable leather materials of a good hiker with an EVA midsole more akin to running shoes. So, you聮ll get good comfort right out of the box. Plus, it has a Gore XCR bootie. The sole is a proprietary Garmont design, but I聮m sure it聮s fine.
Another great boot in this area is the Asolo Stynger GTX ($180; asolo.com). It has sort of a hybrid construction, with uppers made from leather and nylon for light weight and breathability. A Gore-Tex liner keeps you dry. It has a slightly stiffer and firmer midsole than the Garmonts, but it聮s still fine for day hikes and great for light backpacking trips.
If either of these seem a bit over-built for your needs, try a pair of Merrell聮s new Chameleon ARC Mid boots ($120; merrell.com). These are sort of trail-runners with more height, built for women, and very comfortable. Proprietary waterproof booties keep the wet stuff out. They are nice-looking shoes for day hikes and overnighters with light loads.
The 2008 Winter 国产吃瓜黑料 Buyer聮s Guide is now online. From snow sports to trail-running to camping, get reviews of more than 300 new gear must-haves.