To do a DNS Flush on your computer ...

Windows XP:
- Start -> Run -> type cmd
- in command prompt, type ipconfig /flushdns
- Done! Your Window DNS cache has just been flushed.

Windows Vista:
- Start -> type cmd in the 'start search' field
- in command prompt, type ipconfig /flushdns
- Done! Your Window DNS cache has just been flushed.

Mac OS X:
- type lookupd -flushcache in your terminal to flush the DNS resolver cache.
ex: bash-2.05a$ lookupd -flushcache
- Once you run the command your DNS cache (in Mac OS X) will flush.

Also make sure you clear your cache and cookies.
How to delete cookies, clear temp internet cache - Photobucket Forums

After you've done all that, reboot your computer.