Checkboxes on contact form 7 wordpress slow on safari

Checkboxes on contact form 7 wordpress slow on safari. site link is below:

http://ift.tt/1CleH55

click any checkbox in safari mac. and its takes about 5 seconds to load. not sure about what fix to apply or debug why it happens

http://ift.tt/1MFfCOX

you can see proof here