Bug fixing becomes the most crucial activity in the software development process. Fixing bugs accounts a large amount of time of software development task. Sometimes these bug fixes are incomplete or inappropriate and results in bug reopen. Reopened bugs degrades the overall quality of the software perceived by the users and also increases the maintenance costs and indicates instability in the software system. Bugs can be re-opened for a variety of reasons. In this paper, we determined that which factors indicate whether a bug will be re-opened or not using Bugzilla database for Mozilla Firefox. An analysis is performed on components, different severity levels and the last resolution for the trunk version and Unspecified version of Mozilla Firefox to study their impact on bug re-opens. A relationship between significant factors is also established to make the prediction model more accurate. The findings of this work contribute towards better understanding of what factors impact bug re-openings so they can be examined more carefully.