Had this problem with Opera 31. Reinstalling had no effect. Tried going back to Opera 30, same problem ... and the darn thing autoupdates back to 31 anyway.
Went back to Opera 29 ... works fine, and if you download it to a separate folder without deleting the earlier versions (I created one called 'Opera 29') all your Bookmarks are saved.
But autoupdate, which cannot be easily turned off any more in Preferences, continually forced me back to the buggy and useless Opera 31.
Found this solution ... select the icon you boot from, right click (Windows) and go to 'Preferences' ... at the end of the 'Target' box type --disable-update and, voila, it is disabled and you can enjoy no further 'out of memory' errors ...
"C:\Program Files (x86)\Opera 29\29.0.1795.60\opera.exe" --disable-update