Hi Ellen
Due to issues with the Viewer being Free and the architecture if SCN the download of the full Viewer version is contained under the Trial download button. So you have the full released version.
Regarding your bug can you supply some more information? It sounds like the problem is intermittent since you say "The viewer does not always..."
What browser and version are you using?
What type of file are you trying to open?
Does the same file open every time using the stand alone desktop version of the Viewer?
Regards
Paul