Although I am using Arch Linux and not CentOS, in case it helps, I encountered a similar issue with a recent upgrade of firefox (to 33.0.2). The problem looked like a simple case of dependencies that somehow did not get handled properly by the package manager.
The initial problem I encountered when I updated firefox and tried to start it was
XPCOMGlueLoad error for file /usr/lib/firefox/libxul.so:
libicui18n.so.54: cannot open shared object file: No such file or directory
Couldn't load XPCOM.
I tracked down that libicui18n.so.54 is in the icu (International Components for Unicode library) package, so I updated that package. I then tried to start firefox and got
XPCOMGlueLoad error for file /usr/lib/firefox/libxul.so:
/usr/lib/libnss3.so: version `NSS_3.16.2' not found (required by /usr/lib/firefox/libxul.so)
Couldn't load XPCOM.
So, I tracked down that libnss3.so is in the nss (Mozilla Network Security Services) package, so I updated that package too.
Then everything worked.
Apparently this is caused because of incompatibility between Firefox 48 and Selenium(selenium extension is not signed in firefox 48, and firefox 48 only runs signed extensions). I just used chrome, as my use-case was not extremely browser-specific.
Best Answer
Just found out the issue. The above approach works with the older version of firefox (45.0.1) but not the latest one (46.0.1) that would call the libgtk3 and libgdk3. Will carry on using 45.0.1 for now.