It looks like you have the text fields set to medium except for this one, it is set to large. If you set it to medium it should look like the others.
I was able to get the security question text field looking alright by adjusting width of the large style like this:
form.Warren_warrenhome input.formTextfield_Large {
margin:0 0 0 2px;
padding:5px;
width:124px;
}
If you used the formTextfield_Medium style it should match the others on the page.