Button flies off to the right in IE7, have been trying to fix this for ages

I've been trying to fix this bug for ages and have finally turned to StackOverflow for help. In IE7 on https://easygap.co.uk/4/getaquote/ the "Yes" button disappears and flies across the pa开发者_JAVA百科ge to the very right (usually forces scroll too).

Any idea why it would do this and how I could fix it?

Thanks.

I guess the css text-indent: 999px; is one thats causing it.