The header right widget area and the title area are both too wide to fit within that space. One is 50% and the other is 65%…..which exceeds 100% and is the reason one drops off to the side.
To fix this change the title/logo area width to around 32% instead of 50. Look for this around line 681 –
.header-image #title,
.header-image #title a,
.header-image #title-area {
display: block;
float: left;
min-height: 120px;
overflow: hidden;
text-indent: -9999px;
width: 32%;
}