Maybe a Vacuum bug in 6.3.2

Hi...
Gigantic table woes again... I get
sc=> vacuum test_detail;
FATAL 1:  palloc failure: memory exhausted

This is a very simple table too:
| word_id                          | int4                             |4 |
| url_id                           | int4                             |4 |
| word_count                       | int2                             |2 |


while vacuuming a rather big table:
sc=> select count(*) from test_detail;
Field| Value
-- RECORD 0 --
count| 78444613
(1 row)

There is lots of free space on that drive:
/dev/sd1s1e   8854584  6547824  1598400    80%    /scdb
The test_detail table is in a few files too...
-rw-------  1 postgres  postgres  2147483648 May  9 23:28 test_detail
-rw-------  1 postgres  postgres  2147483648 May  9 23:23 test_detail.1
-rw-------  1 postgres  postgres   949608448 May  9 23:28 test_detail.2


I am not running out of swap space either...



under top the backend just keeps growing.
  492 postgres 85   0 16980K 19076K RUN      1:43 91.67% 91.48% postgres
when it hit about 20 megs, it craps out. Swap space is 0% used, and I am
not even convinced this is using all 128 megs of ram either. Could
something like memory fragementation be an issue?


Does anyone have any ideas other than buying a gig of ram?