Welcome to Apple Discussions.
if anyone has any advice please help thanks
To give you the best help, we need some info about the systems and connections involved. Post back and give as much as possible of the information requested in the the When do I Post a New iChat Topic ? FAQ, starting about half way down the page.
By my count, the list requests 19 items of information. You should give the info for EACH system involved. (You may even find the problem in the process of gathering that info.)
In addition, let us know that your OS X Maintenance is up to date, whether you have EVER had a successful video chat on your system, and what (if anything) has changed since then. We will be happy to try to provide more specific responses based on your additional info.
However, if you want to try some things on your own first, here are some ideas.
First, be certain you can meet Apple's stated System Requirements for iChat AV 3
If you need more help than iChat > Help > iChat Help on your Mac gives you, check out the iChat AV Frequently Asked Questions (FAQ).
Although these FAQs were written for iChat AV 2.1, the process is VERY similar in iChat AV 3, but some features and menu commands have changed slightly. The FAQs may not be updated for iChat AV 3 for a while because we are still learning so much.
Start with What do I need to start in iChat ? FAQ.
If you use a router, try enabling its UP-n-P feature. If that does not help, see the How can I get my router to work with iChat? FAQ for further help with configuration.
For additional router info, also see Ralph Johns' GREAT iChat web pages. The sections on Router Set Up and the menu and sub-menu items titled "Setting Up Your Router" and "Eliminating Problem areas" will give you a lot of useful info. (You may want to bookmark Ralph's entire site as a primary iChat AV reference.)
You might also want to review Ralph Johns' current Trouble Shooting thread and Apple's Tiger Support page.
If you are having other problems with your Mac after your Tiger install, Apple's Troubleshooting Mac OS X installation from CD or DVD article may give you some ideas.
Of course, if you have specific questions after reviewing the FAQs and trying these suggestions, we will be happy to try to give more specific answers here based on your additional information.
Alternatively, you might want to look at some of the existing threads or post your own iChat AV questions in iChat AV 3 -Included with Tiger Discussions ".