Hi - haven't come across this error message yet though this is documented behaviour for RCurl, here:
http://www.omegahat.org/RCurl/FAQ.html
Look towards the bottom of the page for the same error message you've reproduced below. Basically you need to make sure that you have a valid certificate installed (eg.
http://curl.haxx.se/docs/caextract.html) to pass to the underlying curl program - or to disable certificate checks. Full instructions for specifying the right certificate are listed at the above URL - ideally you want to make sure that the file curl-ca-bundle.crt is available for your local curl install, as specified in the RCurl FAQs.
Also, see the help info for curl for more details on the same subject:
http://curl.haxx.se/docs/sslcerts.html
Remember that RCurl is just an R wrapper for curl, so if your curl install is good for https pages then so should RCurl be.
Also, note that the SSL library should be installed for curl to work with https connections. You can check that it is by typing
> curl-config --feature
at your system command line - or instead from within R by running the sourceforge access example listed in the
>?getURL
R help function (after RCurl has been loaded by the betfaiR library).