I am running FireFox 2.0, Mass Downloader 3.2.651 SR2 and have downloaded and installed the latest Firefox integrator.
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Please uninstall the current version of MetaProducts Integration plug-in and reboot your browser. Then please install one from: http://www.metaproducts.com/download/L_mpint.xpi
Download DebugView from: http://download.sysinternals.com/Files/DebugView.zip, unpack and run Dbgview.exe from this zip archive. Then go to FireFox and try to start the download using Mass Downloader. The plug-in will print debug log to the DebugView window. Save it to file using File | Save as menu entry and send it to firstname.lastname@example.org with a short description of the problem.
Thank you for your help.