Found the source of the problem. Still haven't found the solution.
The photo I uploaded here, was small by requirements of the forum. So, I tried uploading the same photo to my site. It worked. Then I looked at the photo I was trying to upload. It was some pet photos I took last year with an 8mega pixel camera. The files were 1.9 Meg each. Those won't upload, for some reason. I have automatic resizing.
When I tested my other computer, I didn't have any of those large files and the ones that worked there, were smaller.
So, it appears that I can upload files from my 4 M Pixel camera (800-900K) but not my 8 M Pixel camera (1.9 Meg or so). Must be a setting somewhere for that. I have 1024 pixel width with automatic resizing but I don't see a setting for max photo upload size.
At least I know it's not really with my laptop.
Now, to find a solution.
I'm going now to check each of the options in the photopost control panel.