Thank you everyone for helping me out to fix this, really appreciate..The issue seems to be fixed, checked the server quota, server usage and load on the server but everything was pretty normal.. There was McAfee security installed in the system which was restricting the site to respond, I have uninstalled the software and it seems to be working fine now.

Thank you Karthik and Marko for the response, it worked in IE browser, but why is it creating issues in Chrome? any suggestion...

+1, Thank you very much Lisa, that was really helpful and descriptive.

Thanks for the answer mate. really appreciate it. as you have mentioned in the first point, workflow will not trigger if the script runs with system account, does that mean if we create items in bulk with any other credentials than system account would trigger the workflow? and why is that?