Yes, HK stands for Hong Kong. The general idea was, that HK Dingoos are models for the inner chinese market, but there are many more theories... Big drama when the first unpawed Dingoos were discovered.
How old is your Dingoo? I think you?re the first who actually had the 1.00 firmware, even back in May 09 everybody had at least 1.02 iirc. The first unpawed ones surfaced a few months after i got mine, i?d say July 09, and they all had a higher version number too i think. Maybe (big maybe) you got a prototype Dingoo?
Unlikely, but who knows...
Also you could simply downgrade to 1.03 and then up to 1.22, the updater only checks if the firmware is the same, not if it?s older/newer. Your problems might persist though. Since everything (except the emus) works perfect (does it? radio, tvout, video, music etc.), try the HK emulators.
I must say i don?t get your problem fully, 20% of games ran slower before (1.00), 80% run slower/don?t run now (1.22)?