Memory allocation error

[acampbell]

Quite often I see this when I start vim -g (while running X, obviously):

Gdk-WARNING **: shmget failed: error 12 (Cannot allocate memory)

Googling shows someone with the same error on FSBSD, but no obvious solution.
In spite of the error, vim -g opens and works normally, so I don't know how much it matters. But is there any way to fix it? (Stopping firefox makes it go away.)