Just ran into a problem this morning since opera has been working up to Opera v. 12.
On start-up you get something like this:
captainmoonlite :: ~ » opera Could not initialize Opera.
Running the startup script with strace reveals the culprit:
captainmoonlite :: ~ » strace opera
execve("/usr/bin/opera", ["opera"], [/* 71 vars */]) = 0
[...]
lstat("/home/roman/.kde/share/config/kcmnspluginrc", 0x7fffbd443080) = -1 EACCES (Permission denied)
write(2, "Could not initialize Opera.\n", 28Could not initialize Opera.
After fixing the permissions of .kde/share/config, opera started just fine. Opera v.11 must have not accessed this directory or file. strace FTW!
Romanofskis Blog 
Thanks for posting about this. There will be a fix for the issue in a future Opera Next snapshot.
Cheers!
Perhaps I should have checked and reported it earlier, as I was already having trouble with the v11 beta builds.
This information is very util! Thanks a lot!