In the Settings » Media admin page I set the image sizes as:
Thumbnail: Width 120 x Height 150
Medium: Max Width 224 x Max Height 300
Large: Max Width 380 x Max Height 480
Maximum embed size: Width 380 x Height 600
Yet when I upload an image, the media library only offers me "Full Size."
The "full-size" images that I uploaded were 380x285.
WP v3.1.2 installed on a Windows server.
I have WP v3.0.4 installed on the same server and I am not having this issue.