Just to be sure, when testing [geo_mashup_map map_content="single"] you cleared 
the W3TC cache or disabled W3TC?

I can't reproduce the behavior here. To make progress I think I'd have to do 
some debugging on your site, which means I'd need a temporary admin WP account 
and FTP access. Email me directly if you'd like to try that.

I have the same issue

I figured out where it come from but not how to solve it!

the output from the plugin on your example is:
http://trans-americas.com/blog/?geo_mashup_content=render-map&map_data_key=cf928
f4dab65c0de3d45a44cf6302920

where it shoud be
http://trans-americas.com/blog/?geo_mashup_content=render-map&map_data_key=cf928
f4dab65c0de3d45a44cf6302920

something (probably Jquery) is changing "&" into "&"

the plugin don't understand and send the global map

i think the fix can be the same as what they did for this plugin
see: 
http://wordpress.org/support/topic/plugin-comprehensive-google-map-plugin-seems-
to-cause-a-jquery-script-conflict

I have this issue since i changed my theme
plugin work when i remove wp_enqueue_script( 'ux-jquery' );
but after my theme isn't working anymore

hope it helps

The & encoding is correct in HTML: 

http://stackoverflow.com/questions/275150/xhtml-and-ampersand-encoding

The browser interprets it correctly, which is why the map in the post is the 
one generated by the URL with the decoded ampersand. The problem is not the 
URL, it's the map content, which should have a single marker.

Ok so I may have another issue because when I read the source of the html and 
get the map source and past it in a Web browser it doesn't work. I and when I 
remove the & and I replace it with just &, and it display the map. You I can't 
figure out why

as an example:
http://www.team-decade.com/2011/04/chicago-illinois/

you can see that the map is not rendering what I want, it seems to be the 
global map centered on the last marker

Plugins outpout is:
<iframe name="gm-map-1" 
src="http://www.team-decade.com/?geo_mashup_content=render-map&map_data_key=4763
b7b20400a36d00f70d82f680012c" height="310" width="310" marginheight="0" 
marginwidth="0" scrolling="no" frameborder="0"></iframe>

when i copy: 
http://www.team-decade.com/?geo_mashup_content=render-map&map_data_key=4763b7b20
400a36d00f70d82f680012c
it DOESN'T WORK

when I copy
http://www.team-decade.com/?geo_mashup_content=render-map&map_data_key=4763b7b20
400a36d00f70d82f680012c
it WORK

when I desactivate wp_enqueue_script( 'ux-jquery' ); in my theme it work

Toppa I'm happy to give admin access for debugging.

thanks

I had the same issue and found a workaround. Here is a quick fix:

<?php 
if (GeoMashup::current_location())
  echo GeoMashup::map(); 
?>

No it's no working
i tried to past the iframe in a post without & and it's not working

it's only working when i remove wp_enqueue_script( 'ux-jquery' ); from my theme

the script is registered this way in my theme
wp_register_script( 'ux-jquery', $file_dir.'/js/jquery-1.7.1.min.js', 'jquery', 
"1.7.1", false );

I think that like issue 614, r1189 may resolve this as well. You can try it in 
1.5rc1:

http://code.google.com/p/wordpress-geo-mashup/downloads/detail?name=geo-mashup-1
.4.99.2.zip&can=2&q=