Due to vardiff, you submit higher difficulty shares with faster miner, they are harder to find but cost more. For hashrate display, please mine for 15 minutes as displayed hashrate is averaged over this time.
Been running it for a while now on a separate address, and it's settled in at only 0.04MH/s on
http://hvc.1gh.com.
And my per-block share values are about 1/4 what I'm getting from 2 cpu-mining VMs with a hash rate of 0.16 MH/s.
This makes no sense

Please run it with debug and protocol enabled (-D -P) and PM me some of the output to investigate.
However, most probably it is non-GCN card (hashrate too low), the kernel is known to not work properly on these.