iTunes & Safari Won't Connect to Internet

I have seen posts of others who have had this problem without a resolution in the archives. Has anyone else seen a solution to this:

When using iTunes I can't connect to the Music Store or get podcast updates. Safari will also not connect to the internet. I don't have a problem using Firefox or Microsoft Entourage with my net connection.

I'm currently connected to a wireless high speed ISP through a router, but originally had no problems. Now over the past few months this issue has cropped up. I have installed and used Onyx to correct any permission problems (or so I beleive) but I continue to get the iTunes error and Safari won't even load a page. Any thoughts?

Thank you for your help, this has become quite annoying!