[Plugin: Aweber Comment Optin] background on checkbox in IE

I’m trying to set up this plug-in which seems to be working and looking great in Chrome and Firefox but the checkbox does weird things in IE.

Is there some CSS I could apply to fix the width of the checkbox area? I don’t mind that the grey color appears behind the checkbox in IE as long as the width can be adjusted.

http://wdwprepschool.com/ask-shannon-should-i-buy-park-hoppers-and-do-extra-magic-hours/#comments

http://wordpress.org/extend/plugins/aweber-comment-optin/