Here's what I did to fix width issue; your mileage may vary. I added 2 width statements in the theme.css file (you need to apply this to each them or at least to the one you are using. Here is how it looks:
div.calendar { position: relative; width:22.5em; }

.calendar, .calendar table {
border: 1px solid #bdb2bf;
font-size: 11px;
color: #000;
cursor: default;
background: url("normal-bg.gif");
font-family: "trebuchet ms",verdana,tahoma,sans-serif;
width:19em;

}

Good luck!