I have exactly the same issue. Had 1.21, everything was running perfectly, switched to 1.32NA - "freezes" every 3 days or so. When the router "freezes", it passes through every second DNS request or so, so browsing is really slow. Web management interface is unavailable as well - sometimes it just won't respond, sometimes it returns 0 bytes.
Factory firmware was NA too (i assume, since the device was purchased in US).
No antiviruses of any kind are installed. No p2p software (other than Skype). Issue appears both in Windows 7 (64bit RC with D-Link DWA-160) and Linux (Ubuntu Karmic 32-bit with Linksys WUSB54G v4, no Skype on this box), so it's definitely something with firmware and not driver/NDIS/etc.