Hello, i'm experiencing the same problem with the Sandbox domain
Apparently it's a server error.
Soap request:
---------------------
<soap:Envelope xmlns:soap="
http://schemas.xmlsoap.org/soap/envelope/"
xmlns:xsi="
http://www.w3.org/2001/XMLSchema-instance"
xmlns:xsd="
http://www.w3.org/2001/XMLSchema">
<soap:Header>
<applicationToken xmlns="
https://adwords.google.com/api/adwords/
v12">***</applicationToken>
<clientEmail xmlns="
https://adwords.google.com/api/adwords/v12">***</
clientEmail>
<developerToken xmlns="
https://adwords.google.com/api/adwords/
v12">***</developerToken>
<email xmlns="
https://adwords.google.com/api/adwords/v12">***</
email>
<password xmlns="
https://adwords.google.com/api/adwords/v12">***</
password>
<useragent xmlns="
https://adwords.google.com/api/adwords/v12">***</
useragent>
</soap:Header>
<soap:Body>
<getAllAdWordsCampaigns xmlns="
https://adwords.google.com/api/
adwords/v12">
<dummy>0</dummy>
</getAllAdWordsCampaigns>
</soap:Body>
</soap:Envelope>
Soap response:
-----------------------
<html><head>
<meta http-equiv="content-type" content="text/html;charset=utf-8">
<title>502 Server Error</title>
<style><!--
body {font-family: arial,sans-serif}
div.nav {margin-top: 1ex}
div.nav A {font-size: 10pt; font-family: arial,sans-serif}
span.nav {font-size: 10pt; font-family: arial,sans-serif; font-weight:
bold}
div.nav A,span.big {font-size: 12pt; color: #0000cc}
div.nav A {font-size: 10pt; color: black}
A.l:link {color: #6f6f6f}
A.u:link {color: green}
//--></style>
<script><!--
var rc=502;
//-->
</script>
</head>
<body text=#000000 bgcolor=#ffffff>
<table border=0 cellpadding=2 cellspacing=0 width=100%><tr><td
rowspan=3 width=1% nowrap>
<b><font face=times color=#0039b6 size=10>G</font><font face=times
color=#c41200 size=10>o</font><font face=times color=#f3c518
size=10>o</font><font face=times color=#0039b6 size=10>g</font><font
face=times color=#30a72f size=10>l</font><font face=times
color=#c41200 size=10>e</font> </b>
<td> </td></tr>
<tr><td bgcolor=#3366cc><font face=arial,sans-serif
color=#ffffff><b>Error</b></td></tr>
<tr><td> </td></tr></table>
<blockquote>
<H1>Server Error</H1>
The server encountered a temporary error and could not complete your
request.<p>Please try again in 30 seconds.
<p>
</blockquote>
<table width=100% cellpadding=0 cellspacing=0><tr><td
bgcolor=#3366cc><img alt="" width=1 height=4></td></tr></table>
</body></html>