METRO Web Service client does not respond

METRO Web Service client does not respond

Hello, dear users!
We have some troubles with performance of Java METRO web service client.
The web-service client is a part of a web application, it is not a desktop
program (maybe it is important). It is deployed on GlassFish 3.1.2, the OS
is 32-bit Windows Server 2003 SP2. The client performs a high number of
requests to the web-service (which is another web application on a
different machine) - sometimes hundreds of requests in minute.
The problem is that occasionally (4 or 5 times a day) the web service
client stops responding and hangs (without any exceptions thrown). In the
TCPView we can see lot of processes started by the web-service client.
When the problem first occured, we specified minimal WS client timeout
values, but the issue still persists (probably the container does not
dispose connections?).
Could you please suggest what can possibly be a source of the problem?
Maybe we should change the keep-alive http value, or something else? I
understand that the description of the problem is not very detailed, but
unfortunately I do not have any ideas how to begin the investigation.
Thank you in advance!