Invalid file hash
If you receive the error, Firefox could not install the file at <URL> because: Invalid file hash (possible download corruption) when clicking an "Install" link, try the following:
* Reload the page or clear the Firefox cache: "Tools -> Options -> Advanced -> Network / Cache -> Clear Now" (Firefox 2) or "Tools -> Options -> Privacy -> Cache -> Clear" (Firefox 1.5), then try again. [6]
* If installing from addons.mozilla.org, the problem could be with the addons.mozilla.org database (bug 345505) or a broken mirror site (bug 420278). Try restarting Firefox to see if the extension or theme was installed despite the error [7]. You could also try installing at a later time or from an alternate location such as the author's homepage [8].
* Manually install the extension (right-click the install link -> "Save Link As"-> save the .jar or .xpi file, then drag the file icon onto an open Firefox window). Note: If a manual install also fails, an antivirus (or other software that monitors downloads) may be corrupting the file. You could try saving the file on another computer, then copy it over and manually install it on the problem computer. [9]
