It appears to be too large for the space you are trying to insert it into. The Fastastic theme has a maximum displayed image width of 544 pixels. See note at in the post I link to below.
Maximum displayed image width
Most themes have a specific width limit (measured in pixels) for images inserted in a post or a page. Obviously, that limit depends on the theme’s main column width (which varies greatly from theme to theme). If you exceed it, the image may be cut off, or overlap the sidebar; in a few themes it may become distorted or even break the theme. Read more> http://wpbtips.wordpress.com/2009/07/23/maximum-image-width/