Well you are runing a PCIe card 2.0 in a slot 1.0 x16, which means in theory that it will run at half of the performance it should... did try istaling it into another rig? or any other card into your PCIe slot? maybe thats the problem...
PCI 1.1 x16 isn't going to be saturated by a GT 240. I had a 5850 that ran full speed just fine in a PCI 1.0 x 16 slot. Either the card is a fake or something is wrong with it.
OP, check the power saving settings in the nVidia control center, set to max performance and try rechecking your GPU stats with GPUz. That will make force the GPU to run full speed even under a 2D load and should report the settings as if a 3D load were being run.