I shoot also volleyball, often in poorly lighted sport halls. I have a K-7 with is less performant than the K-x at high ISO, and I have a few tricks to shoot VB without flash.
First technique: i shoot with ISO up to 3200 and I PP the photographs on computer in terms of using PDCU or Noiseware. Both give good results, but I prefer the feeling of Noiseware.
Second technique: use a fast prime. I shot VB with a VL58mm f1.4, a FA31mm f1.8, Tmaron SP90mm f2.8 and a CZ85mm f1.4. Using the largest aperture (f1.8 ot 1.4), I get my best results. I typically work in MF mode + Hi continous shooting. I set the focal fistance manually and I shoot a burst at a time. This works nicely when I sit along the lines. Knowing that the court is 9 m by 9m, it is easy to set the right focal distances.
Another technique with fast MF lenses (f1.4) is to use Catch in focus (CIF) with Hi continuous shooting.
Altogether I got my best keepers using MF + Hi continuous shooting wide open with a fast prime (f1.4). I enclose two examples below. (All taken without flash off course!)
Hope that the comments will help.