WebCam : Frame rate VB.NET=12/s, Flash=28/s

Hi,
Using Flash I can have a frame rate about 28 fps, but I do not exceed 12 fps using VB.Net.
I use avicap32.dll functions. Same using CallBack functions then a Timer event.
I test all internet sources I could find, but no one do better... even if they parameter a fast frames rate...
Where is the solution?
Thanks.

12fps doing what? Previewing the video? Capturing the video? Streaming the video?

Previewing, I mean.

SendMessageCBFrame(New IntPtr(HWnd), WM_CAP_SET_CALLBACK_FRAME, New IntPtr(0), delCallBackFrame)
SendMessage(HWnd, WM_CAP_SET_SCALE, 1, 0)
SendMessage(HWnd, WM_CAP_SET_PREVIEWRATE, pRate, 0)
SendMessage(HWnd, WM_CAP_SET_PREVIEW, 1, 0)