I am encountering the same issue. Using the HTML editor, not the Visual. Copied below is the message I just sent WordPress Support. Anybody have any ideas?
I did:
Went to a Google Map that I created:
http://maps.google.com/maps/ms?ie=UTF8&hl=en&msa=0&ll=18.340024,-77.512922&spn=0.037558,0.034633&t=h&z=15&msid=208549682198117587615.00049ca436b950e9f0d70
and used the "Link" link to get iframe code to embed in my website:
<iframe width="425" height="350" frameborder="0" scrolling="no" marginheight="0" marginwidth="0" src="http://maps.google.com/maps/ms?ie=UTF8&hl=en&msa=0&ll=35.101934,-95.712891&spn=64.25716,70.576172&t=h&msid=208549682198117587615.00049ca436b950e9f0d70&output=embed"></iframe>
<small>View The Alps, Jamaica in a larger map</small>
I pasted this code into the HTML view of the page editor of one of the pages on my website, then clicked Update.
I saw:
The iframe code was turned into a shortcode:
[googlemaps http://maps.google.com/maps/ms?ie=UTF8&hl=en&t=h&msa=0&msid=208549682198117587615.00049ca436b950e9f0d70&ll=18.453557,-77.518158&spn=0.455936,0.583649&z=10&iwloc=00049ca4478fbcd6f1eb7&output=embed&w=425&h=350%5D
But when I view the page, nothing appears below the title; the shortcode produces no output.
I expected:
To see an embedded Google Map in my page. I have done this on other WordPress sites with essentially the same procedure, and it seems to work intermittently; I can't figure out what makes it work and what makes it fail.