There are a lot of things that could be causing that. Look at the things I'll list here, maybe you can solve it quickly. If not, post more information.

How is the FPS if you view the cam from a browser on the local AbelCam machine? If it's okay there, there's something about the network slowing things down.

What FPS are you trying to achieve? In theory you can go up to 30, in reality 5 is a more reasonable number. You did set the desired FPS in the Capture Device config dialog "Framerate" box, right?

What resolution are you using? Big images obviously take more CPU, USB bandwith and network bandwidth than little ones. 320x240 is a nice resolution for testing, 640x480 is probably okay for production, anything bigger can easily saturate a cable connection or even the USB bus.

How is the CPU load looking? Unfortunate fact of life is that video processing eats lots of CPU. But if you're seeing a CPU load of more than about 25% for one cam, you may need to reconsider your resolution selection and/or kill off some unrelated processes.

If there is a lot of stuff hooked up to USB it is possible that either a) the bus is bogging down (saturating) or b) the Sphere's driver is using its "Reconsider Bandwidth" feature to slow itself down and "protect" the USB bus. Check Imaging Devices -> QuickCam in Device Manager to see what the driver is up to. It doesn't provide a whole lot of info but at least you can see if Reconsider is on (and turn it off).

Is the scene that the camera sees brightly lit? If the light is not bright enough to satisfy the camera, it will reduce its shutter speed to compensate, which will in turn reduce the framerate that the cam sends to the software. I have had bad cases of that here: a cam that does 10 FPS just fine in daylight slows down to 2 - 3 FPS at night.

If you can't solve it with any of the above, post answers to the questions I mixed in with the suggestions and maybe I can be more helpful.