Yes, I have found out that it can be due to the browser am using. Am using Google Chrome, which I have been using all along and it was working fine until recently. I tried Internet Explorer and it worked fine with the pdf file and default name rightly generated for saving. So the issue could be due to some setting or changes in my Chrome browser. Thanks @lubos and @Tut
When problems are reported that turn out to be browser-caused, they are almost always traceable to Chrome.