NWDI debug thread not responding

Hi all,

ISA 5.0 application working fine in dev system. 

In QA the same application stucks at checkout.inc.jsp page and do not continue on button action and do not display next page confirm.jsp, instead it displays checkout.inc.jsp page itself.  When I debug ISA application in QA, the NWDI debug thread hangs and debug thread becoms "not responding".  It hangs at Action code after click on button in checkout.inc.jsp.

The same application worked fine earlier and the issue shows up suddently.

Please let me know if anything that I have to check in this regard.  Thanks in advance to all of you.