You need to follow the Gmail help instructions carefully, especially:
1) enable POP3/SMTP access of your account. They are disabled by default.
2) Setup correct port for POP3 and SMTP server. They are different than commonly used.
I am using Outklook 2003 and Outlook Express to access Gmail account and never got problem.
The Gmail Team is committed to making sure you always can access your mail. That's why we're offering POP access and auto-forwarding. Both features are free for all Gmail users and we have no plans to charge for them in the future.
POP, or Post Office Protocol, lets you download messages from Gmail's servers onto your computer so you can access your mail with a program like Microsoft Outlook Express or Netscape Mail, even when you aren't connected to the Internet. Learn more.
With auto-forwarding, you can redirect some or all of your messages to another email account, automatically. Auto-forwarding is different from POP access because you need to sign in to another email account to access the Gmail messages you've redirected. Learn more.