Servers show "---" ping if they aren't port forwarded properly and use UPnP.
Unfortunately, UPnP has some problems.
Some users (including you) can't connect to servers with it:
http://forum.blockland.us/index.php?topic=265922.10Can you look into Blocklands options under Network and see if UPnP is turned on?
I don't know if that will fix it.
You can also try connecting to those servers from a different location.
It is possible the problem lies with your own router, that it doesn't support UPnP.
Or it might be a firewall issue.
So Try turning it off for a minute.
UPnP needs a port opened, although I doubt it needs to be on your side.
But try anyway.
The only other thing you can do is ask the server host to port forward.