Stubborn upload error on new IIS installation

Gallery URL (optional but very useful): unfortunately internal
Gallery version:1.5.6
Apache version: N/A, on IIS
PHP version (don't just say PHP 4, please):5.2.3
Graphics Toolkit:ImageMagic 6.3.3.5
Operating system: IIS6 on Windows Server 2003
Web browser/version (if applicable):

I'm migrating my existing Gallery1 to new hardware so that I can then upgrade to Gallery2

For the life of me I can't get uploading to work. I have read every post, FAQ and documentation that I can find and none seem to address the issue I'm seeing. From what I can from the debug messages, the image doesn't seem to be even uploaded prior to manipulation (and I've confirmed the image doesn't appear in the file system) I've given the folder system as much permissions as I can, and still no joy... I even blew away the server and started again, and the same issue occurs.

Processing status...

******Adding test.jpg*****
Album.php::1161 -> Doing the naming
Album.php::1194 -> Image Preprocessing
Album.php::1199 -> Resizing/compressing original image
imageManipulation.php::36 -> Resizing Image: D:/InetPub/gallery/albums/album01/test_001.jpg
util.php::208 -> Getting Dimension of file: D:/InetPub/gallery/albums/album01/test_001.jpg
util.php::211 -> The file does not exist ?!
imageManipulation.php::67 -> No resizing required
imageManipulation.php::580 -> Call to getimagesize() failed in valid_image() for file D:/InetPub/gallery/albums/album01/test_001.jpg!

Error: Invalid image: test_001.jpg

Any help appreciated!! Can post whatever other debug messages are needed.