HELP restarting postmaster

Our server went down unexpectedly. I restarted postgres using
"postmaster -i &" but now I can't access any existing databases
or create new ones. When I run "psql blc" I get the following
error messages:

$ psql blc
IpcSemaphoreCreate: semget failed (Invalid argument) key=5432114,
num=16, permis
sion=600
Connection to database 'blc' failed.
pqReadData() -- backend closed the channel unexpectedly.
This probably means the backend terminated abnormally before or
while pr
ocessing the request.

Any help would be much appreciated. I posted elsewhere first but never
got a response.

-Anne Rose
Human-Computer Interaction Lab
University of Maryland