does anybody heah know if theres a codec to make kdenlive support avi and flv

Could you give some more info please? Which distribution are you on? Which version of Kdenlive?

im using ubuntu and version 6.0

There is no version 6.0, neither of Ubuntu nor of Kdenlive. ;)

In Kdenlive, go to "Help -> About Kdenlive" and post which version is written there.
On the Ubuntu desktop, open "System -> About Ubuntu" and post the version of Ubuntu specified there.

ubuntu version 8.10 intrepid kdenlive 0.6.0

Ubuntu's multimedia packages for 8.10 intentionally restricted codec choices. There is no simple package to install to fix this. All you can really do is upgrade to 9.04 or 9.10 and install the "unstripped" versions of the ffmpeg packages to get the additional codecs. But if you do this, you will also need to upgrade Kdenlive, for which there are directions on the Web site and in the forums.