Internet stops working frequently on OS X Lion After upgrading to Lion, I started experiencing this issue:  

Internet stops working frequently.
- I open Safari and browse for some time
- Suddenly I can't open any sites; Internet will stop working.
- So I check WiFi; it is online and showing correctly in my MacBook Pro.
- I check with my roommate and his Internet is working properly.
- I switch to Google Chrome and it still doesn't work.

The solution is to turn WiFi off and back on, then restart my browser.

Does anyone else have this problem? Is this a bug?
This is currently a known issue that lots of Lion users are reporting. The average seems to be 2 wifi dropouts per hour.

The current work around is (as you discovered) to toggle AirPort on/off.

This particular issue seems to be getting alot of attention so I'd expect a fix soon.

Apple support forum topic about this issue