Step 1: Install RHEL 6.2 using Platform HPC 3.1.
Apart from the Platform HPC 3.1 extra packages, there are no custom changes to the RHEl 6.2 distribution nor updates at this point.

Step 2: Packages installed.
kernel-2.6.32-220.el6_lustre.g4554b65.x86_64.rpm
kernel-debuginfo-2.6.32-220.el6_lustre.g4554b65.x86_64.rpm
kernel-debuginfo-common-x86_64-2.6.32-220.el6_lustre.g4554b65.x86_64.rpm
kernel-devel-2.6.32-220.el6_lustre.g4554b65.x86_64.rpm
kernel-firmware-2.6.32-220.el6_lustre.g4554b65.x86_64.rpm
kernel-headers-2.6.32-220.el6_lustre.g4554b65.x86_64.rpm
lustre-2.1.1-2.6.32_220.el6_lustre.g4554b65.x86_64.x86_64.rpm
lustre-debuginfo-2.1.1-2.6.32_220.el6_lustre.g4554b65.x86_64.x86_64.rpm
lustre-ldiskfs-3.3.0-2.6.32_220.el6_lustre.g4554b65.x86_64.x86_64.rpm
lustre-ldiskfs-debuginfo-3.3.0-2.6.32_220.el6_lustre.g4554b65.x86_64.x86_64.rpm
lustre-modules-2.1.1-2.6.32_220.el6_lustre.g4554b65.x86_64.x86_64.rpm
lustre-source-2.1.1-2.6.32_220.el6_lustre.g4554b65.x86_64.x86_64.rpm
lustre-tests-2.1.1-2.6.32_220.el6_lustre.g4554b65.x86_64.x86_64.rpm
perf-2.6.32-220.el6_lustre.g4554b65.x86_64.rpm
perf-debuginfo-2.6.32-220.el6_lustre.g4554b65.x86_64.rpm
python-perf-2.6.32-220.el6_lustre.g4554b65.x86_64.rpm

Step 3: Computer rebooted.

Step 4: Run lctl set_param debug_mb=10
[root@storage000 ~]# lctl set_param debug_mb=10
debug_mb=10
error: set_param: writing to file /proc/sys/lnet/debug_mb: Invalid argument
[root@storage000 ~]#

[root@storage000 ~]# cat /proc/sys/lnet/debug_mb
121
[root@storage000 ~]# echo 10 > /proc/sys/lnet/debug_mb
-bash: echo: write error: Invalid argument
[root@storage000 ~]#

This error is reproduced every time after following the steps above.