IPC Problems - URGENT !

Hi all
    I am in a fix right now - i have been trying to install Postgres
6.4.2 on Linux ( Calderra Open Linux).
    Everything goes on fine - i.e. configure,installation  etc.

   At the time of starting of the Postmaster ( postmaster -S -D 'Data
Directory'), I get the following error :

    IPCMemoryCreate : shmget (identifies removed) Key=5432010
size=24588, permission =700 .
    IPCMemoryAttach : shmget (identifies removed) Key=5432010
size=24588, permission =0 .
    IPCMemoryCreate : shmat failed (invalid argument) id=2 .
    FATAL 1 : AttachSLockMemory : could not attach segment .

It will be really very kind of you if you could help me out.

Thanks in advance
Thyaga