Your corner css is probably going to look something like this:

{ border-radius: #px #px #px #px; -khtml-border-radius: #px; -webkit-border-radius: #px; }

When those #px have the same value, it becomes a circle. (In mine, for some things it's 9px 9px 9px 9px.) The higher the number, the more of a curve it has - 0px is a square edge. If yours is curved-and-angles, you probably have something that looks like 9px 0px 9px 0px -- just change all of them to the same (higher) number.