When using pop-overs, like the lightbox version of your AWeber form, it is overlapped by flash elements.
The default behavior for flash means that it will always overlap any sort of HTML attempting to be layered on top of it. Fixing that so that pop-over forms appear correctly above the flash requires an easy modification to the way flash videos are embedded on the website.
There are two elements you need to add to your video code to override this issue.
Add <param name="wmode" value="opaque" /> directly after your opening "object" tag.
Add wmode="opaque" within your embed tag.
Here is an example of how your video code might look with the fix in place:
How do I fix my form to appear above flash content?