I have been using a plugin using jquery-1.2.1.min.js, I want to now use another plugin on my site that uses http://ajax.googleapis.com/ajax/libs/jquery/1.3/jquery.min.js

I replaced the reference to the jquery file but the original plugin no longer works, it will only work with 1.2.1.

Is jquery upgradable in this way or do plugins use specific features of a specific version?

The plugin is the lightbox plugin http://leandrovieira.com/projects/jquery/lightbox/ (which uses 1.2.1) but I now also want to use the tab slide out plugin http://wpaoli.building58.com/2009/09/jquery-tab-slide-out-plugin/ (which uses 1.3)

Thanks