Running on a Snow Leopard MacBook air, can't browse the web (in any browser, tried FF,Chrome,Safari) using DNS names that are either already cached in DNS or not. Browsing to google.com or thisisnotincache.com both result in the browser reporting a "not connected to the internet" page. Ok, DNS resolution we're all thinking...nope. Terminal I can ping, trace, nslookup, and everything else all of these DNS names (those that exist in cache, those that don't, flushing cache, etc. all still resolve just fine) on all DNS servers. Still, browsing in a web browser DOES work if I use actual IP's as the address rather than a DNS name (i.e. http://188.8.131.52) works just fine. Even more odd, I pull up Terminal and try using Curl to "browse" by DNS name, and that works just fine (in addition to by IP).
I've triple checked proxy settings (and none are being used anywhere on any network), I've tried using different DNS servers, I've removed all filter drivers that were there (i.e. software VPN, Firewalls, etc.), and turned of nearly everything I can think of that would even remotely possibly contribute to anything.
Naturally, I'm now running a malware/virus scan to be thorough, but that's been running for an hour with nothing found yet, though who knows.
[EDIT]: Some additional info in response to comments. Yes, rebooted, no luck. Verified proxy settings (no proxies anywhere, OS level, browser, etc.). Other applications are working fine (skype, dropbox, email apps, etc.). Literally, all I can seem to find that isn't "working" is browsing the web with any web browser by DNS name.