Need help with Table of Content

Hi,
I have recently started working with Robohelp 7. I just completed my first project working with the tool. This project has several Topics, and each topic has sub-topic under them. When I generated the html files, I had given the Introductory sub-topic as the default topic.

Now after the files are generated, I cannot open any other topic in the table of content until I expand the topic containing the default sub-topic. This issue is basically with Firefox browser. It seems to work well with Safari. IE anyways opens the folder containing the default topic.

I am not sure if any other user have faced similar problems? Would like to hear from you guys too.