Found this on thewitcher.com website FAQ page (
http://en.thewitcher.com/support/#q22):
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Graphical issues in cutscenes or dialogues up
For Nvidia graphic card users
Please install drivers 275.33 or newer.
As for ATI graphic card users
Please install Catalyst 11.5b (or newer) drivers hotfix and latest Catalyst Application Profiles fromhere. NOTE: It is advised to uninstall previous version of Catalyst Application Profiles before installing new version.
If problem still persists please turn off "Depth of field" and "Blur" option in graphic settings.
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So far it worked to get me through the final dragon battle. It seemed to turn off the interactive parts of it and just let it play through (no more useless mouse button mashing at certain points).