I updated to v29 yesterday--4/29/2014. A 1.5 vertical right strip blacked out appeared on the far right of the browser page. Moving the cursor sometimes caused the whole page to black out or the part it was over to black out. I reset to default. The right black strip is gone, but the other problem is worse--in addition to parts of the browser blacking out I now have flashing black areas. The bug, at least for my computer, needs to be fixed. If not, is there a way to upload the previous version. Firefox has been my principle browser for years. I can no longer use it, until the problem is fixed or I upload an earlier version. (I am writing this from a different browser.)