problem with NVIDIA CUDA C SDK(Video Encode and Decode.

I’m now researching H.264 GPU encoding solutions . I tested the NVIDIA CUDA C SDK(Video Encode and Decode)
but it can only start 8 Encoder process .
The API NVCreateHWEncoder return Failure when I start the 9th the encoder process.
i do not know why it happened.My GPU is GeFore GT240.

thank you for your reply.

Probably running out of memory ?