Stuttering video

[Voice for Peace]

Keeps getting worse on my computer -- not for dvd's
but all streaming video.

I thought it might be an age-related problem but am reading
that even brand new Macs are having this problem.

I have NOT come across a fix.. have restored permissions,
rebooted, let it cool down, upgraded, mackeeper'd, etc.
Some things have seemed to work but only very short-term.

Any answers? It's frustrating, can usually watch no more
than 2-3 minutes at the most before stuttering starts.
Thanks for any help!