Shared memory problem

Ok, thank you for your help with initdb. This week I was having this
problem from time to time, and I have to reboot Linux in order to fix
it. Any ideas?

010123.15:16:54.659  [3943] IpcMemoryCreate: shmget failed (Identifier
removed) key=5432010, size=144, permission=700
This type of error is usually caused by an improper
shared memory or System V IPC semaphore configuration.
For more information, see the FAQ and platform-specific
FAQ's in the source directory pgsql/doc or on our
web site at http://www.postgresql.org.
010123.15:16:54.671  [3943] IpcMemoryIdGet: shmget failed (Identifier
removed) key=5432010, size=144, permission=0
010123.15:16:54.672  [3943] IpcMemoryAttach: shmat failed (Invalid
argument) id=-2
010123.15:16:54.672  [3943] FATAL 1:  AttachSLockMemory: could not
attach segment

Leandro.