DirectSound Reading Data From Capture Buffer?

where I'm going wrong with my circular DirectSound Capture buffer here? If I just capture sound into a big non-circular buffer it works fine, but with a 1 second (44100 bytes) buffer and a 100ms timer to poll the read position it goes haywire. No error messages, just long blocks of zeros with short bursts of valid data. calculation of the number of bytes to read and/or the read position.

Here is the code. gBuffer is defined elsewhere as a big byte array. In this example I am just trying to copy the captured sound data from the small temporary byte array (tempBuffer) into the big gBuffer byte array. Obviously this must be done so that every byte is read and copied into the byte array with no gaps or duplication of values. Timer1 is set to 100mS:

Dim McaptureBuffer As CaptureBuffer
Dim MiLastReadPos As Integer
Dim MiBufferOffset As Integer

[Code].....