this is more a javascript problem than a css problem.
the issue is that the map is created when the page loads. It is created using the height and width of the containing object at load time, your jQuery is changing that height and width so the map is not created to the correct dimensions.
to fix the problem, find the following line of code in the google_javascript/wagmp_map_1.js file:
var map = new GMap2(document.getElementById('wagmp_map_1'));
and change it to:
var mapElem = document.getElementById('wagmp_map_1');
var mapWidth = mapElem.style.width;
var mapHeight = mapElem.style.height;
var map = new GMap2(document.getElementById('wagmp_map_1'),{size:new GSize(mapWidth.replace('px',''),mapHeight.replace('px',''))});
