contact 7 plugin stops some pages from working properly

It’s not the Plugin that is at fault, but the Theme.

The Theme enqueues a custom version of jQuery, which you should never ever do. Also when the jQuery plugin is initialized, you need to use noConflict wrappers like this:

jQuery(document).ready(function($) {
    // Inside of this function, $() will work as an alias for jQuery()
    // and other libraries also using $ will not be accessible under this shortcut

I assume that Contact Form 7 uses jQuery as well, but since the Theme does it wrong, this causes a conflict.