libnss3.so => not found
libsmime3.so => not found
libssl3.so => not found
libplds4.so => not found
libplc4.so => not found
libnspr4.so => not found
These weren't found.
Why it works with shiretoko, I guess it includes those libs in its own directory. And why Flash requires some Mozilla libraries (libplc4 for example), when it's supposed to be browser-agnostic..
See if starting opera from a shell like this helps:
LD_LIBRARY_PATH=/usr/local/firefox/firefox-3.5.6 opera