Pixelated video and upscaling problems with ringing artifacts on Youtube since Flash player 10.3. Flash palyer 10.2 was the last version without the listed problems.
For anyone interested you may see here what 'ringing artifacts' means : http://en.wikipedia.org/wiki/Ringing_artifact
More about Image artifacts/errors related to video scaling here : http://en.wikipedia.org/wiki/Video_scaler
Test configuration :
Windows 7 x64
Intel HD Graphics with lastest available drivers from manufacturer.
Any solution from Adobe?