can't create a database

everything else seems ok. add tables, add records.
but when i try 'create database tt;' interactively or do 'createdb tt'
in shell, i get:
Server process (pid 446) exited with status 11 at Wed Oct 17 17:04:06
2001
Terminating any active server processes...
Server processes were terminated at Wed Oct 17 17:04:06 2001
Reinitializing shared memory and semaphores
DEBUG: database system was interrupted at 2001-10-17 17:01:24 PDT
DEBUG: CheckPoint record at (0, 2271516)
DEBUG: Redo record at (0, 2271516); Undo record at (0, 0); Shutdown
TRUE
DEBUG: NextTransactionId: 797; NextOid: 67890
DEBUG: database system was not properly shut down; automatic recovery
in progress...
DEBUG: ReadRecord: record with zero len at (0, 2271580)
DEBUG: redo is not required
DEBUG: database system is in production state

the folder 67890 is created with a lot of files, but new db isn't in
system catalog. next time i try to create a db with a different name
shell says:
ERROR: CREATE DATABASE: unable to create database directory
'/usr/local/pgsql/data/base/67890': File exists
createdb: database creation failed

any one have a clue?