I have tryed reinstalling the software sevral times, in addition I have also tryed installing and reinstauling (all after successfull uninstulations, of corce.) on an external Hard Drive. The error is not intermitant after it appers and dose not go away, even after a reinstulation. I notice that only after a system restore and fresh copy ofinternet phone, new instulation, dose the error go's away. I have repeted this process sevral times to see if I can find a patturn. I notice that the error begins occering after one or both of the fallowing two conditions occure, wether the instulation is on my pc or on my external HDD (hard drive): 1) After downloading the therd catalog and before starting the forth catalog download within Stellarium, than closing the software fallowed by restarting windows than relaunching the software. 2) After canceling a previously started download of a catalog within Stellarium. Note: In both cases, the error dosen't always occer right away.