recurrent tramp hangs with non-tramp usage

[Seb]

Hi,

I'm experiencing hangs when, for instance, trying to compose a mail
message (hitting 'm': gnus-group-mail).  Emacs hangs for several
minutes, with a message in the minibuffer:

Tramp: Waiting for prompts from remote shell

Eventually it gets out of the hang, and checking the *Messages* buffer,
I see:

---<--------------------cut here---------------start------------------->---
Tramp: Opening connection for ssh using scpc...
Tramp: Sending command `exec ssh   -o ControlPath=/tmp/address@hidden:%p -o 
ControlMaster=yes -e none ssh'

Tramp: Waiting for prompts from remote shell
Tramp: Sending command `exec ssh   -o ControlPath=/tmp/address@hidden:%p -o 
ControlMaster=yes -e none ssh'
Tramp: Opening connection for ssh using scpc...done
Tramp: Opening connection for ssh using scpc...
Tramp: Sending command `exec ssh   -o ControlPath=/tmp/address@hidden:%p -o 
ControlMaster=yes -e none ssh'
---<--------------------cut here---------------end--------------------->---

The buffer *tramp/scpc ssh* buffer shows:

ssh: Could not resolve hostname ssh: Name or service not known

Process *tramp/scpc ssh* exited abnormally with code 255

Any tips what may be going on?  Thanks.

Cheers,

-- 
Seb