I have just drawn a masterpiece in PsP. Saved as a PNG. Imported into Vegas. It will only "show", against its torquiose BG, if Level is less than 100%. Otherwise I have a screen full of torquiose. Never seen anything like this.
What resolution/dpi is the Photoshop piece. Sometimes, higher res graphics like 300 or higher dpi, won't appear when placed on a timeline. Although it's crappy for print, 72dpi is the standard resolution setting for a lot of video.
But, to give dave a little credit, if the pixel dimensions of the image are too large then maybe Vegas will get a little wonky. That's the technical term, right?
"Contrary" is a good one. "If you do XYZ, Vegas will become contrary, argumentative, uncooperative, disagreeable, petulant, hostile, vengeful, or spiteful."
None of this is helping Grazie, though, so here's a general list of things you can do to an image file that might cause troubles in various NLEs:
--File's dimensions are too large
--File's header information is not what the application expects (Header too long, Header contains unknown tags, too much metadata, etc.)
--File is in CYMK mode
--File is in greyscale mode
--File has an unexpected bit depth (16-bit PSD file, for example)
--Application that created the file did so in a non-standard way (I think Photoshop 6 made nonstandard PNG files, for example)