Problem viewing forums or other content

Hi, I'm a newbie so go easy-ok? I have an old imac and a powerbook. Both are running the same OS 10.3 I can use the powerbook from wifi to be in SL. Sometimes at home (dial-up) i just want to view the forums or other content here. I can login fine but then i get a message that i have to login when i click on forums, I AM logged in-the webpage shows "welcome Phoenix Nohkan"
After clicking the forum link i get sent to a page where i get the message about having to have logged in once and also another about updating payment info-however i can view the forums and other content fine from wifi spots and-it gets stranger-a friend brought her pc laptop over today and I can login and view the forums and other content from her computer-which I'm doing right now. Why is this happening and what can i do about it? Thanks.

Hello Phoenix
So basically in a nut shell
Platform is: iMac and Powerbook running OS 10.3
WiFi works fine getting to SL
On Dial-up accessing secondlife.com web page - main page on the upright hand corner you see "Welcome, Phoenix Nohkan"
Then you click on Community then Forums.
Then you get a page that reads:
vBulletin Message
You must 'log in' to view the Second Life forums.

If you recieve this error after successfully logging in to other parts of the Second Life website, please make sure that:
• You have logged in to Second Life at least once with your account.
• You have valid payment info on file for your account, if your account was created after August 20, 2006. You can update your payment information here.
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Have you tried clicking on the 'log in' link on this page. You should come to a page to enter your Avatars name and password?
- Two thing I would recommend - delete the Secondlife.com preference file.
Located in the User Name / Library / Preferences / com.secondlife.indra.viewer.plist (or do a search on the file name) and move it to the trash.
- Don't logout of www.secondlife.com just close the window. When you come back it should show you as logged in.