Android : Android 504 Gateway Timeout

I m actually facing a problem while using Spring Framework for android.

When my user is connected, I need to get a list of task that he has to do during the day. I ask my webservice (working great with wifi) but when I need to use it with 3G/Edge network it doesnt work and give me a :

org.springframework.web.client.HttpServerErrorException: 504 Gateway Timeout

The connection with wifi takes ~3 seconds, and after 20-30 seconds in 3g/e and it crashed...

Any idea ?

Thanks for advance