PostgreSQL 6.4 problems on Linux.

Hi,

I upgrade postgres to 6.4, compile and install postgres with no problems. But
when I run
postmaster -i&, I got the following messages:

% IpcMemoryCreate: shmget failed (Invalid argument) key=543200
1, size=831176, permission=600
FATAL 1:  ShmemCreate: cannot create region

I don't know what's wrong with it, would anyone tell me how to fix this problem,
thanks.
The kernel version is 2.0.35.

P.S. I run 6.3 with no problems.

Thanks in advance,
Kevin.