Bug or local setup C-w but not C-y in group buffer

[Harry Putnam <reader@newsguy.com>]

First a brief explanation:

I've switched over to using slrnpull for my main server and reading
with nnspool.  So far, coolio mundo.

I thought I'd use my regular NNTP server as a foreign server and
subscribe to a number of groups I previously kept above:
(setq gnus-agent-handle-level 3) and put them back in that capacity.

`B' in group buffer and get the list from my `old' nntp server. 
Painstakingly subscribed to some 20 groups or so.
Letting them accumulate at the bottom of group buffer.

Now to place them where I like them in the group buffer, I expected to
be able to use C-w after setting the region, and C-y to plop them down
where I wanted them in one move.  It ain't happening.

C-w works fine, but C-y doesn't and throws an error something like:
Wrong type argument ..blah blah stringp blah....

So now I've got the twenty groups C-w 'ed but can't get them
back. Undo doesn't help either.

I have to go into `A K' (killed groups) and find them, resub and move
them with C-k/C-y.

It seems to me its a bug to have C-w work but not C-y.  Either both or
neither would be more usefull.