Unable to upload photos, chat, see messages etc. in Facebook.

Hello. I am having serious trouble with my facebook account. I have a MacBook Pro OSX 10.5.8 and I use Safari and Firefox browsers. Most of the time facebook will open, but I do occasionally have trouble opening it. If it opens, I can not upload images or chat or read messages / events etc. It just continues to load forever and then prompts me to open ai.php or login.php file. After many failed attempts of running anti-virus software and trying my best to clean up the computer, I accepted the ai.php and still nothing works.

All other accounts / sites work. Facebook is the only problem.

Any advice would be greatly appreciated.

Thank You!