I'm not sure if this method is going to help in all the situations, but after following it I now have a 100% working (yupeee ;-) ) Roboform toolbar (my version 7.1.1) on my Firefox4!. So if you want to know how to fix roboform not working issue in Firefox4, then this is how I was able to "fix" it.
1. If you're upgrading from Firefox 3.6 + to the new version 4 -
Then I advice you to do the upgrade but then make sure to reboot the PC. This most of the time may help to fix that issue, but if it doesn't work then follow the instructions starting below or you can try go directly to the "Blue" sub heading.
2. Do fresh/clean install of Firefox4 -
*. First make backups of your Bookmarks and other data of your current Firefox 3.6 or whatever the version that you're using. Then uninstall it. I used a windows registry cleaner called CCleaner, which is free utility that cleans your registry and history, etc. If you don't like it then you don't have to use it, but it is worth a try. You can install it and run it. Then from the left menu of its GUI, choose "registry" tab and from that new option click on "fix selected issues" button on the right below area.
It'll do some registry cleaning and when done you can reboot your PC (you can skip using CCleaner if you want to).
*. After your PC boots back to the desktop, now first install the Firefox4.
*. Then install your Roboform software and since we have already installed Firefox, it should automatically install the "adapter" which embeds its functions via the web browser automatically).
*. Again do a reboot and when come back to desktop run your Firefox and see if your roboform tool bar is working. If still it does not work then follow the below instructions.
*. Now Open the newly install Firefox4 and go to the menus on the browser to
Tools -> Addons
And from addons window, choose the "extensions" tab on the left side.
*. After clicking that you'll be listed all installed extension on your Firefox. Now from that menu you'll see an extension called "AI Roboform for Firefox yourversion". Click on the "disable" button.
*. Now close Firefox and don't reopen it (yet).
*. Open your Roboform manager or click on the small looking roboform icon close to your notification area and click on it, from the menu, choose "Options".
*. From the Options window, click "Firefox" from the left.
*. Make the sure the "Attach Roboform to Firefox even if Adapter is not installed", option is activated. If not, click on to activate it and then click "OK" on the menu to close the window.
*. Now open Firefox4 and the toolbar should be working. If not try rebooting your PC and run Firefox again. Also make sure you've activated the roboform toolbar on Firefox (View -> Toolbars -> Roboform Toolbar).
If that doesn't work for you either, then I guess you'll have to wait till Roboform give you an update.
Note - Make sure you're using the latest Roboform manager, if not, update it (click on the roboform notification icon to get the menu and go to, "Help" -> "Check for Updates").