I'm having an issue installing OpenMotif on RHEL5 x86_64. I need to run MSC Patran and it requres 2.2.3, but RHEL5 comes with 2.3.1. I tried to build it from source, but I get the following error during the make:

makestrs.c:51:21: error: X11/Xos.h: No such file or directory

Thank you for any help you can give,

Fritz