1. Did you follow the advice above? (uncheck both checkboxes under "Administration center > Plugins > Event Logger > Options)
2. Have you tried disabling all non-default plugins? (some plugins can be disabled by unchecking their checkbox under "Administration center > Plugins," for others you may need to move the plugin directory out of the $Q2A_DIR/qa-plugins directory)
3. Have you tried profiling a slow operation with your browser's web development tools to identify the bottleneck? If so, what were the results?