Hi,
You shouldn't have to specify '--x-column=X' and '--ycolumn=Y'; those are the defaults.
That command-line looks fine. If you look on the
nova.astrometry.net result page, click on the "Submission #####", and go down to the log file listing, what index does it say it solved with? Do you have the equivalent one?
And I hope the --ra,--dec you're giving are actually within half a degree of the right answer ;)
cheers,
--dustin