Mysql seems to be using only 1 core (1 reply)

I got mysql 5.1 running on Ubuntu and all the mysql threads seem to be wanting to go over the same core. For example if I run a query which will take up to a minute to process, all the other querys from different connections will wait for this one to complete. At this moment also only one of the cores sit at 100% while the other 7 cores in the machine basically do nothing.

What can this be?

Here is my my.cnf
[client]
port = 3306
socket = /var/run/mysqld/mysqld.sock
[mysqld_safe]
socket = /var/run/mysqld/mysqld.sock
nice = 0

[mysqld]
user = mysql
pid-file = /var/run/mysqld/mysqld.pid
socket = /var/run/mysqld/mysqld.sock
port = 3306
basedir = /usr
datadir = /var/lib/mysql
tmpdir = /tmp
skip-external-locking
skip-locking
skip-name-resolve
key_buffer = 16M
max_allowed_packet = 16M
thread_stack = 128K
thread_cache_size = 8
thread_concurrency = 16

innodb_thread_concurrency = 16
myisam-recover = BACKUP
query_cache_limit = 1M
query_cache_size = 16M

expire_logs_days = 10
max_binlog_size = 100M

skip-federated
set-variable = max_connections=2000

[mysqldump]
quick
quote-names
max_allowed_packet = 16M

[mysql]

[isamchk]
key_buffer = 16M