After finally getting fed up with constant Shock Wave errors on the most recent stable build ( using osx 10.9.4) ( and it happened no matter what other programs i had open or if it was one tab or many tabs) I sat down to take a look at this problem and this is what i did which has proved to work so far ( tested for about 4 hours of use on Facebook which is where i was seeing this almost exclusively)
First I checked into /Users/USERNAME/Library/Application Support/com.operasoftware.Opera And looked int he LIB section of Extensions. The only thing I found to be out of place was 2 extensions that were labeled Chrome( which i have never installed) so i went ahead and trashed those 2 files.
I've experienced similar issues in the past when using opera next but that was with java, and i remembered how I had fixed that on my own so i thought I'd try it out for this issue as well.
~Steps to fix~
I searched out the Adobe Flash removal tool and found it here: uninstall_flash_player_osx.dmg Please note this is for 10.6.8 and higher older versions have a different version, which you can find on your own.
You will need to make sure all web browsers and system preferences are closed before you run this, Just to be Sure, I recommend Going to your apple logo int he top left and choosing Force Quit and closing out of everything open (finder stays open all the time so skip that one) Run the Uninstall tool and then Reboot your machine, it make take some extra time to start up this round as it has to save the changes it made, I then opened my System preferences and made sure Flash was not showing any longer. After I opened Opera and verified that Facebook and other locations I had see the issue previously, was no longer crashing. Went to the Adobe Site, downloaded the Flash player ( made sure to uncheck the extra content they wanted to give me) and then installed. Once it was done i rebooted once more, opened opera and everything was fixed. I've had several tabs open for the last few hours and so far not a single hiccup, side note opera seems to be a bit lighter on it's feet as well.
Hope this Helps everyone!