What OS are you using? Looks like Windows, but what version? Do you have a dialup, broadband or other kind of internet connnection? Do you connect through a proxy? Is your computer's connection through a router?
Have you changed any of Firebirds setting?
Just checking all the angles. I tried and have been using Firebird, along with Opera on XP and have not run into this problem. Please let us know if this continues.