you know I honestly have no clue at this point since ie's inspect element is terrible. I think the code you used to layout this portion of your website is not a 100% correct, therefore differences between browsers will appear in the future. i took a look at ie7 as well as ie8 and its definetly not a 100% the same.
Ill you could upload the fixed versions, i or someone else could take a look and try to find some things. you may have used some css that isn't ie7 supported. that's my only guess at this point
just a word of caution:
will only be implemented in ie versions. however i believe your site was fine in ie9. so you may want to consider an ie7 stylesheet
<!--[if IE 7]>
<!-- overflow: visible code -->