[CentOS] High l-avg with centos 4.8 on G2 only

Hi

We deployed centos 4.8 on HP DL380 G2, G3 and G4 servers (same number of cpus). The same software is running on all servers.
Only on G2 servers we see a low cpu utilization combined with high load-average.
For example, during the same time of day and same workload, on a G2 I see a l-avg of 11.31 and on a G4 I see 2.68.

The server response time seems unchanged and we don't have any problem with it so far, but I need to figure out why the l-avg remains high.
We were running redhad AS 3 before, and the l-avg was low on all server type.

Anyone have an idea where I should look.
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