Hi Steve, could you clear Firefox's settings for opening PDFs? Somehow that seems to have been set to a dysfunctional behavior. You can try changing it on the Options page. If that doesn't work, you'll need to remove a settings file. '''Options Page''' * Windows: "3-bar" menu button (or Tools menu) > Options * Mac: "3-bar" menu button (or Firefox menu) > Preferences * Linux: "3-bar" menu button (or Edit menu) > Preferences * Any system: type or paste '''about:preferences''' into the address bar and press Enter/Return to load it Scroll down to the Applications section. You can type ''pdf'' in the bar above the list to filter it. The following settings should be safe: * Preview in Firefox * Always Ask * Save File * Use Adobe Acrobat (this refers to an external application) * Use Adobe Reader (this refers to an external application) Avoid anything like "Use Firefox" because it can cause an infinite loop of new tabs or new windows as Firefox keeps getting told to open itself to open the PDF. '''Remove Settings File''' If the first method didn't work: Open your current Firefox settings (AKA Firefox profile) folder using either * "3-bar" menu button > "?" button > Troubleshooting Information * (menu bar) Help > Troubleshooting Information * type or paste about:support in the address bar and press Enter In the first table on the page, click the "Open Folder" button. This should launch a new window listing various files and folders in Windows Explorer. Leaving that window open, switch back to Firefox and Exit, either: * "3-bar" menu button > "power" button * (menu bar) File > Exit Pause while Firefox finishes its cleanup, then right-click > Rename '''handlers.json''' to something like handlersOLD.json. Start Firefox back up and default PDF behavior should be restored ("Preview in Firefox").

Thanks Jscher2000