I was trying to install the Grid Control on my Enterprise Linux 5.3 on VMware and I got the error

  Checking operating system version: must be enterprise-4, enterprise-5, redhat-3, redhat-4, redhat-5, redhat-5.1, SuSE-9, SuSE-10, UnitedLinux-1.0, asianux-1 or asianux-2

All installer requirements met.

Preparing to launch Oracle Universal Installer from /tmp/OraInstall2009-06-04_08-58-48PM. Please wait ...

$ Exception in thread "main" java.lang.UnsatisfiedLinkError: /tmp/OraInstall2009-06-04_08-58-48PM/jre/1.4.2/lib/i386/libawt.so: libXp.so.6: cannot open shared object file: No such file or directory
        at java.lang.ClassLoader$NativeLibrary.load(Native Method)
        at java.lang.ClassLoader.loadLibrary0(Unknown Source)

Checking the operating system:
$ uname -a
Linux DG1 2.6.18-128.el5PAE #1 SMP Wed Jan 21 08:28:30 EST 2009 i686 athlon i386 GNU/Linux

[root@DG1 ~]# cd /usr/lib
[root@DG1 lib]# ls -l libXp*
lrwxrwxrwx 1 root root    16 Apr 30 21:30 libXpm.so.4 -> libXpm.so.4.11.0
-rwxr-xr-x 1 root root 69316 Jun  6  2007 libXpm.so.4.11.0
There is already a soft link with libXpm*, let's create a second one
[root@DG1 lib]# ln -s libXpm.so.4.11.0 libXp.so.6
[root@DG1 lib]# 

So, creating a soft link fixed the error; what's next?

Checking for the Hostname...
Check complete. The overall result of this check is: Failed<<<<
Problem: The host name in /etc/hosts is not proper.
Recommendation: Please verify the hostname in /etc/hosts.
The /etc/hosts might either contain short host name or ip address instead of full host name
This is because I called the server DG1; I will rename it to grid10g
Checking for required packages installed on the system ....
Checking for make-3.79; found make-1:3.81-3.el5.	Passed
Checking for binutils-; found binutils-	Passed
Checking for gcc-2.96; found gcc-4.1.2-44.el5.	Passed
Checking for openmotif-2.1.30-11; found Not found.	Failed <<<<
Check complete. The overall result of this check is: Failed <<<<
Problem: Some required packages are missing.
Now, if I try to install openmotif-2.1.30-11 from the CD 3, it complains because libXp.so.6 is missing despite the link.
The Oracle metalink informs that the rpm xorg-x11-deprecated-libs-6.8.1-12.i386.rpm is required to resolve the libXp.so.6 dependency.

I found it on http://www.filewatcher.com/m/xorg-x11-deprecated-libs-6.8.1-12.i386.rpm.247178.0.0.html
Now, even if there is no libXp.so.6 on /var/tmp, openmotif-2.1.30-11 installs. Isn't it funny?
Well, it's not, the dependencies are satisfied by some other path that does not include libXp.so.6

Lesson learned: install xorg-x11-deprecated-libs-6.8.1-12.i386.rpm and no package will complain about libXp.so.6