Be carefull with installing the latest Flash Builder 4.5 (Burito) beta. It comes with a flash player that can damage the debugging process in Flash CS5. If you installed the Flash Builder Beta your CS5 Flash Player might show one of the following behaviours:

  • Random crashes of the internal preview – only on the debug player, the IDE keeps running stable
  • Colors might be displayed wrong, for example you have a grey background on an object and it gets displayed as white

If this happens to you, replace your Flash Player Debug Player as described by Adobe.