Many reasons could be causing this - the more likely are:
The distance and power settings of the Wireless access point (WAP) and/or laptop are not adequate for sustaining an authenticated session for any length of time.
The two wireless NICs may be containing the same type of chipset and the chipset driver(s) may be buggy.
The WiFi access point may be locked down in more ways than one (MAC Nos, domain authentication).
DNS server access may only be allowed for authenticated clients and your friend's machine does not authenticate successfully.
Can you get it to work (first associate, then obtain an IP address, then ping an Internet website) if you move the laptop closer to the WAP - like within a yard or so?