Firefox iMacro Add-on Error (0x8000ffff NS_ERROR_UNEXPECTED)

I was running iMacro Add-on for Firefox on a Linux machine. iMacro reported the following error,

Error: NS_ERROR_UNEXPECTED: 
  Component returned failure code: 0x8000ffff (NS_ERROR_UNEXPECTED) 
  [nsIPrefBranch.getIntPref], line 6 (Error code: -1001)

I tried the same script on two Linux machines, the same error occurred. The versions of the two cases are as follows,

• iMacros for Firefox 8.8.2
• Firefox 33.0
• Ubuntu 14.04

A few others saw the similar problem, as reported here in Feburary 2014.

To verify the problem exists, you may run the demo script coming from iMaco add-on, such as, Loop-Csv-2-Web.iim by default at $HOME/iMacros/Macros/Demo-Firefox. In my case, running the demo program would yield the same error.

Apparently, no fixes exist. One suggested workaround is to use an old version of Firefix, as indicated in the discussion mentioned above.

We can download old versions of Firefox from here. I tried Firefox 27.0b9. It works fine with the iMacro demo scripts and my scripts.

Since you would probably have another copy of Firefox installed, it is important that you close all existing Firefox window and run the older version of Firefox using its path. In addition, it is also important to check "Never check for updates (not reocmmended:security risk)" from the Preference under the "Advanced" tab; otherwise, the old Firefox would automatically download updates and the updates would be applied when the old Firefox restarts. Below is the list of steps that I performed,

wget https://ftp.mozilla.org/pub/mozilla.org/\
firefox/releases/27.0b9/linux-i686/en-US/firefox-27.0b9.tar.bz2

tar -xjvf firefox-27.0b9.tar.bz2

firefox/firefox -preferences # disable updates

firefox/firefox