It seems that a few of the external FTP programs that I have used have created a permissions problem under Vista. When the Yawcam saves an image, and the FTP (yawcams) goes to grab that image at the same time the image is being written, it generated a permissions problem where the image is stored., resulting in a error.
I discovered this problem while using other FTP programs to send the locally saved image under Yawcam. I selected the properties for the file and set it to "share". So far, the problem is gone. (About six hours now).
I hope that helps explain the problem. This is only under Vista.
Here is a rather detailed, and frankly overdone example of how to set things up http://technet.microsoft.com/en-us/library/bb727037.aspx
My Yawcam has been running for three days with no errors, no lockups. Smooth. (Three days now)