Q:

JSON response not sent

I have two servers. Server A and server B. I use php, jquery for the programming language, Apache for the web server.
What I want to achieve:
There are javascript that call this url http://serverB/someprocess.php, server B response with json whether the process 'someprocess' is TRUE or FALSE
Problem:
When I test locally, it works just like I want. But when I upload the script, and when I look at firebug, there are no JSON response from server B, so the script fail.
Question:
I had many problem about script work in local but in live before, but this one really confuse me. What should I check? Can you give me any clue?
Note: 
'someprocess' is a php script that do process transferring data from progress DB (not postgre) via Merrant ODBC to SQL Server 2000 and it took 70 seconds to finish
What I have try:

set apache timeout to 80 seconds
change server B response to text

A:

the problem is cross domain ajax request 
a solution is like :
jsonp 
or 
proxy way

