GPU Throttling During Movie?

[PC_User]

I have had my card overclocked with MSI Afterburner for some time now. I just loaded GPU-Z and noticed that my card appears to be throttling between different 2D/3D modes and power states when I watch a movie on the computer (screenshot below).

Oddly, if I'm watching a video online for example, it stays constant at 500/1250MHz which is what I would expect. When watching a video on the PC it jumps from 250/150 to 500/1250.

Any clue on what could be causing the clocks to fluctuate when a movie is playing?

 

[Araxie]

Only happens while OC?... You watching the movie directly on the main HDD or from a Slave?.. This can affect a bit... Also happens with the same movie? You tryed with others?..

Pd: i can not see the img btw...