Tried this with RC4 and RC5.

Ping through an interface works for me with winbox as I would expect. But when I try it though the terminal, I can't seem to get it to work.

[admin@MikroTik] > /ping 64.69.34.1
64.69.34.1 64 byte ping: ttl=53 time=34 ms
64.69.34.1 64 byte ping: ttl=53 time=29 ms
...

but
[admin@MikroTik] > /ping 64.69.34.1 interface=wlan1
64.69.34.1 ping timeout
64.69.34.1 ping timeout

default route is through wlan1, and it works using winbox.

Brian