Try putting the tags in <dc:subject>

Manic, I tried that first, and when it didn't work I moved to the new format of <category>... I checked Nathan's feed over at InsideGoogle and his did work with Technorati, so I copied from the syntax:
http://google.blognewschannel.com/feed/rss2/

See if adding an autodiscovery tag for your feed to head section and then pinging Technorati does the trick..

Strange. I had this auto-discovery tag in my head section, I will fix that. I must have accidentally removed it. Great tip Manic!

Hmm. I went to the Technorati Ping form, submitted, waited, and then I got a default white-page error message.