What exact build of Opera do you have and for which processor?
It is perfectly possible to run Flash in Opera. Check the forums in the my.opera.com community web site.
If you happen to run 64 bits, check
http://www.linuxquestions.org/questi...ls+opera+flash
The reason that both Seamonkey and Mozilla crash as well makes me suspicious about the stability of the rest of the installation.
jlinkels