do you have libstdc++.so.6?
if firefox is what you want to install there are a couple of threads around here about not being able to install firefox ( the one from mozilla.org ) due to 10.1 shipping with libstdc++.so.6 and firefox needing libstdc++.so.5 ( this is due to 10.1 shipping with gcc 3.4 and firefox being built with a gcc 3.2 or 3.3).
One way around this ( this is just a quick and dirty workaround really
) is go and download the firefox binary from mozilla.org. next, google for a libstdc++.so.5 rpm (don't install it). install firefox ( make note of where the firefox-installer directory is going). then, open up the libstdc++ rpm and copy the libstdc++.so.5.0.6 ( the 6 on the end may be a little different) into the firefox-installer folder. and lastly, make a symlink to it ( ln -s <path to firefox-installer>/libstdc++.so.5.0.6 <path to firefox-installer>/libstdc++.so.5).