check your gprs settings.
use a web [internet] gateway.
--> web.orange.com
not wap.orange.com
you should encode your request, so there is no space in it
-->
http://test.yodel.de/test.php?foo=my super foo // wont work
-->
http://test.yodel.de/test.php=foo=my%20super%20foo // should do
check the headers of your request
content-length... etc...
some server cannot handle the request without....
keep on trying!