`J Y' `g' and denied nnimap servers

[Steinar Bang <sb@metis.no>]

I used to have 
  - an nntp primary server
  - a list of secondary servers consisting of 
    - nnml (reading from the local spool file)
    - an nnimap server only reachable from the work network and not at 
      home.  This server had its full DNS name as the servers name and 
      no nnimap-address setting
  - two nnimap servers created in the Server buffer 
  - all three nnimap servers were put under agent control in the
    server buffer
  - all nnml groups are on level 1, all nnimap groups are on level 2,
    and all nntp groups are on level 3 (the default)

With this setup I was able to use `D' in the server buffer to deny all 
nnimap servers, and then do `g' and `J s' to get new articles and
download them using the agent.

Right now I have
  - an nntp primary server
  - a list of secondary servers consisting of 
    - nnml (reading from the local spool file)
    - the work nnimap server tyr (UoW)
    - my home nnimap server doohan (Cyrus)
    - the work nnimap server neptun (Exchange)
    - the work nnimap server apollo (Exchange)
  - all four nnimap servers have a short name and the full network
    name in nnimap-address fields.  All four are put under agent
    control in the server buffer.
  - all nnml groups are on level 1, all nnimap groups are on level 2,
    and all nntp groups are on level 3 (the default)

At work I can see all machines and everything works (more or less.  It 
got stuck occasionally yesterday, but today was flawless).  At home I
have tried denying tyr, neptun, and apollo by using `D' in the server
buffer, but then Gnus gets stuck doing either `J s' or `J Y'.

A strange thing is that after a while there seems to be nnimap servers 
with both the short and the full name in the server buffer.  The
servers with the long name don't go away when Gnus is unplugged.

Does anybody have any ideas what I can do to effectively disable the
work machines while at home?  Is `D' the wrong thing?

Should I instead make all groups on work servers be level 4 and always
do `C-u 4 g' at work? (do I need to prefix `J Y' and `J s' as well?
Do they understand prefixing with the level?)

Is there a completely different way?

Thanx for all and any tips!