The Firefox 3.6.15 update was just released like 36 hours ago (which you used to post here), where do you get the idea that there is a 3.6.16 version available now?

Are you trying to install a development version of Namoroka 3.6.16pre that you found somewhere?

I opened my Mozilla Firefox browser, and was prompted to update. So, I simply followed the instructions. As the update was installing, it stalled while "checking add-on comptability." When I clicked cancel, Mozilla opened as if the update had been installed. So, I just went about my business.

However, the following day, after I had left my browser open for a while, another prompt appeared stating I had downloaded the necessary update, but it hadn't been installed. So, again, I followed the steps and had the exact same issue with the add-on comptability.

I definitely think I saw 3.6.16, however my memory isn't great and it seems more likely that it would have been 3.6.15.

I don't know if that clarifies things for you, but I'm n00b and can't really offer much more than that.