MySQL crashes when InnoDB variables uncommented in my.cnf

We have changed one of our databases to InnoDB, after doing this we tried to uncomment the following in the my.cnf file and restart mysql:

Uncomment the following if you are using InnoDB tables

innodb_data_home_dir = /usr/local/mysql/var/ibdata
innodb_data_file_path = ibdata1:2000M;ibdata2:10M:autoextend
innodb_log_group_home_dir = /usr/local/mysql/var/ibdata
innodb_log_arch_dir = /usr/local/mysql/var//

You can set …_buffer_pool_size up to 50 - 80 %

of RAM but beware of setting memory usage too high

innodb_buffer_pool_size = 512M
innodb_additional_mem_pool_size = 20M

Set …_log_file_size to 25 % of buffer pool size

innodb_log_file_size = 128M
innodb_log_buffer_size = 8M
innodb_flush_log_at_trx_commit = 1
innodb_lock_wait_timeout = 50

After doing this we cannot start mysql.

We are running:
MySQL 5.0.45
PHP 5.2.5
Apache: 2.2.6
FreeBSD: 6.1

The server has a gig of RAM.

If we comment out the InnoDB values in my.cnf again and restart mysql everything works fine accessing both InnoDB and MyISAM tables.

Any advice would be much appreciated, as we need to optomize the server to handle a decent amount of traffic.

If I run SHOW ENGINES in mysql, InnoDB is set to YES.