It's n easy fix if you edit the CSS located at App_Themes/dashcommerce/common.css
Change the .textbox rule as follows:
.textbox { font-size: .75em; height: 1.2em; }
html>body .textbox { font-size: .7em; }
The first increases the height just slightly, and the second decreases the font for Firefox (and other compliant browsers) but not for IE.
This is the solution I'm currently using for this problem;
Also apply these same changes to the rules for .smalltextbox & .longtextbox that should do the trick!
HTH