Steve,
Sorry for the delay in getting back to this. The problem has to do with how we render that button. We have 2 spans, one for the 'in' and the other for the "Login with LinkedIn" text. In the position you're showing that in, the width is too small for both, so the browser is wrapping it.
The simplest fix looks to be adding the following to your template's CSS file:
.jLinkedLogin {
width: 155px;
}
That will force the width to 155px for the whole button regardless of it's container.
Another alternative is to use your own custom image for the Login with LinkedIn button.
I hope that helps, but let me know if you need anything else.
Thanks,
Alex