this does not happen often for me but when it does I just download the current version from the RT extensions page <
www.rockettheme.com/extensions
> and install it manually and then future updates work fine. I am not sure what the hang up is but it happened with various extensions from various companies for me, not just RT extensions. This leads me to believe it is a Joomla issue but I am not sure of that.
Thanks for the tip - we did that and the updates were successful, but all three components still show up in the Extension Manager: Update listing as though they still need to be updated. But in the Extension Manager RokBooster is listed as v.1.1.8, Roknavmenu is v2.0.3, and RokBox is v2.0.4 - the latest versions.