tsearch trouble

I made, installed and tried to use tsearch with no problems up to the point of trying to populate an index. It consistently crashes like this...

LOG: server process (pid 27797) was terminated by signal 11
LOG: terminating any other active server processes
LOG: all server processes terminated; reinitializing shared memory and semaphores
IpcMemoryCreate: shmget(key=5432001, size=29769728, 03600) failed: Cannot allocate memory

This error usually means that PostgreSQL's request for a shared
memory segment exceeded available memory or swap space.
To reduce the request size (currently 29769728 bytes), reduce
PostgreSQL's shared_buffers parameter (currently 3500) and/or
its max_connections parameter (currently 21).

The PostgreSQL Administrator's Guide contains more information about
shared memory configuration.

LOG: database system was interrupted at 2003-02-28 11:18:08 PST
LOG: checkpoint record is at 2/217EBADC

I have no doubt that I have done something stupid, but where should I start looking? I used the right version of source, and followed the instructions...

Thanks!

Ian

Postgresql 7.3.1, NetBSD 1.5.2