I had same problem with Opera 55 and less (Windows 8 and updated drivers). There was slow Opera loading (about 1 minute) and taskbar icons flickering. Today I've installed latest Opera version and removed all files from path "c:/Users/MyUser/AppData/Local/Temp" - not sure it is good practice but there was over 4000 files and almost 2GB of usage. After that opera starts normal (in seconds) and there's no flickering icons.
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