The K-5 can record 1080 video only at 25 fps, but it can do 720 video at 30fps.
If you have certain fluorescent lights that run off of 60 cycle current (like in the U.S.), you may have a frame rate mismatch with the light source at 25 fps. This will sometimes show up as a weird throbbing of the light in the video. (Remember, in a DSLR, the sensor doesn't record the entire image at once, but does it line by line. This is known as a "rolling shutter," and means that parts of the image will be temporally displaced. This will cause some of the image to be exposed when the lighting interval is at its brightest, while other parts of the image will be recorded when the light is at its dimmest.)
As other users have suggested, try shooting in natural light (or a non-cyclic light source, such as tungsten, halogen, or LED) to see if you still have the same problem.
Last edited by jimby; 11-28-2011 at 12:54 AM.