I'm fairly certain that the reason it's not validating is because there is a div within a 'p' tag, but even so I can't figure out how to get rid of the 'p' tag. Any thoughts would be greatly appreciated!
IMHO, being strict with w3c validation is overestimated. It's good to run your site through validator to fix some problems you might have not noticed, but using any complex combination of technologies and trying to make your website fast is bound to get you w3c invalid status sooner or later. The only thing important is that you know why the problem is there and what's its impact on page rendering. Heck, google.com homepage has 39 errors.
Can you change the gallery div from a div to a span? That would "fix" it. You should be able to locate the source code somewhere in your theme. You can assign display: block to the span in CSS to emulate div behavior.
Invalid code can trigger Quirks mode. Quirks mode can cause browser inconsistencies which leads to ( <choke, gag> ) IE conditionals and all sorts of unnecessary tricks. One error away . . . pretty close. :-)