memory grab causes machine to grind to a halt

[Silvio Levy]

I work mostly at home on a laptop, but I keep a window open at all
times at my employer's ssh server. It runs emacs and I do some of my
work inside it (usually in shell-mode).

Problem: when that window dies, emacs remains alive and often -- days
later -- it suddenly starts grabbing memory, causing the server to
grind to a halt until the process is killed somehow.

Any idea what emacs may be doing?  (Note that this is always a process
that's no longer interactive.)

Alternativately, any suggestion for automatically killing the rogue
emacs process *before* it takes up all the memory? For instance, how
to limit it to 50% of available memory?

Thanks,

Silvio