two webcam error

[stockton]

Dear All~~
I want to add two VLDSCapture object to show two webcam video.
If I use two webcam at the same time.
It always have the same error message (ESLException with message 'Can't start capture. -2147942431 - 8007001F').
How can I use two webcam at the same time?

note: I use XE6 and install VisionLab_VCL_7.6.1.0


Thanks.