VirtaulDub Error The source image format is not acceptable. (error code -2)

Hello,
This is first error that I had on my computer. On my system I have Windows Vista 64bit. As a movie fan I collect movies.
For the compression I have installed VirtualDub and AutoGK (automatic installation without any modifications).
Now when I run video compression error message pop up.
Please help, I never had this error message.
Thank you
Jacob

VirtaulDub Error
Output compressor error: The source image format is not acceptable. (error code -2)
OK
