Hi,
If you could, please provide a URL when reporting issues like this, it helps if I can see the problem.
I’ve never found a consistent solution for the infowindow scrollbars. It seems to depend on some combination of the browser, font and other CSS.
Google has several bug tickets open about it, but here’s the most recent. You can “star” it to raise its priority with Google:
http://code.google.com/p/gmaps-api-issues/issues/detail?id=5713
Here are some things to try that may help:
1. Make sure all of your images have a width and height specified, e.g.:
<img style='width:150px; height: 150px'/>
2. Switch to using the custom MapPress “infobox” (you can set it in the settings or in the shortcode with iwtype=”ib”). The infobox resizes properly
3. Enclose your the marker body in a div with a fixed height and width, e.g.:
<div style='width:300px;height:300px'>Your body here</div>