On CentOS5, I'm seeing the 'top' command showing a hover between 20% and 2% idle, but then the load says 1.20. How can that be possible? When I type 'uptime', as well, I see 3 load numbers that are generally around 1.20 - 1.35.
Things like waiting on I/O don't take any CPU time but can block other processes from running.
Maybe you have a process in uninterruptible sleep (process state "D")?
They don't really contribute to load per se while they're sleeping but they are a constant process on the run queue thus the load is artificially inflated.