I haven't had any problems doing cvs updates for quite a while.
But they seem to be back -- just now, I got several

   # cvs -q update -P -d
   ssh_exchange_identification: Connection closed by remote host
   cvs [update aborted]: end of file from server (consult above messages if any)

and one

   # cvs -q update -P -d
   ? distfiles
   ? wip
   fork failed
   Resource temporarily unavailable

while trying to update pkgsrc.