I've been receiving an increasing number of queries on making Googlebar Lite and CoLT compatible with the Firefox 3.1 / 3.5 beta builds. Allow me to explain why they are not yet compatible.
It has been an unofficial policy of mine to wait until new Firefox builds reach a 'release candidate' level of completeness before updating my extensions. My main motivation for doing this is a desire to make as few superfluous updates as possible. If I update the extensions now to work with the current beta builds, I'll have to update them again to work with the next beta (if there is one), and yet again to work with the final release candidates. This kind of rigorous update schedule is annoying, in my opinion, so I'm going to wait. One update, to make them 3.5.x compatible.
If you absolutely want to use the beta Firefox builds, and you can't wait for me to release a fully compatible version of each extension, check out this workaround for forcing compatibility. It's easy to do and allows you to extend to your heart's content.