Hi there.
I recently added a new widget area to the header area of the homepage of my site. Shortly after, I noticed that only some of the header banner images were showing up, and sometimes, just a blank banner appears. This had not happened before. I think this may be related to the new widget (vSlider), but I am not entirely sure, and don't know how to fix it.

Here's some additional info:
Atahualpa 3.7.10
WordPress 3.5
The new widget area is running four vSlider 4.1.1 widgets
Website: http://www.sweetcareersconsulting.com
The error does not seem to happen on individual posts or pages - the vSlider widgets do not appear on any of those pages, which is what led me to think this may be causing the issue.

Would anyone be able to offer any suggestions? Thank you!

1) flush your cache
looks like you may have changed some images as there are now not found, but the cache still points to them

Thank you for the suggestion. I'm running WP Super Cache and cleared that. But the issue remains.
I have 7 images in the /blog/wp-content/themes/atahualpa/images/header folder. I have them set in Atahualpa settings to rotate at 12 second intervals. However, only 2-3 images are appearing on the homepage and appear varying intervals. All images appear at the right intervals on other pages and single/archive post pages.

disable ALL you plugins at the same time and see what happens.

I'm sorry it took me so long to reply. Life got a bit nutty. I tried deactivating all my plugins at once. The header began to work normally, again. When I turned on just the vSlider plugin, the header stopped working correctly again.

sounds like a conflict with the plugin - have you asked the plugin author or looked for another plugin?