It seems to me that you’ve got something in your “.rootrc” and/or “rootlogon.C” which creates problems.
Actually, “root -n” should disable the execution of logon and logoff macros, but just to make sure … remove (rename) your “${HOME}/.rootc”, then “cd” to any subdirectory in which there are NO “./.rootrc” nor “./rootlogon.C” and then try to run “root” (you should get NO errors).
One more thing … how exactly did you build and install your ROOT (I mean all command lines that you used)?
Try to run (there should be just one shared library and one rootmap …):
locate libCore
I’ve found an old thread with a similar problem: X11 problem