Can you post some more information on your Wifi cards? Chipset data is really what we need. Run these commands and post the output:
lspci | grep 802
lsusb | grep 802
Also, remember that NDISWrapper is a last resort in terms of functionality. It basically stuffs Windows drivers into the Linux kernel and hopes for the best. Functionality issues and instability are often problems with NDISWrapper, and usually cannot be solved very easily.