I just bought a new Sony Vaio NS110E (Vista Home Premium) and
experienced the same problem connecting wirelessly to DI-514. My router
setting was NO encryption. Searched a lot on internet and couldn't find
a solution.
However, after I tried to set the router to WPA-PSK encrypted with a
passphrase and set the computer's wireless encryption type to
WPA-Personal TKIP encryption, suddenly the wireless connection works. So
it seems that the router's non-secured or WEP secured options have issue
with Vista.
To allow the router secured by WPA, you have to update its firmware
from D-link's website, and reconfig the router from an XP computer wired
to it.
Hopefully this reply can help some other guys like me to avoid spending
hours on solution search.
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zchen66