This is curious... So far I haven't been able to connect to SSH through 3g data connections either. [ ... ] Until your comment I just though that gprs0 interface was blocked in iptables (don't know how to check that) while wlan0 was not.
iptables -S
EDIT: With not getting connection through 3g I meant timeout, not restriction to log in (as is configured in /etc/sshd_config).