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Over and over again, when using Firefox browser, a window pops up with the message:

Unresponsive script: xpcomutils.jsm:357

which is normally followed by another popup window stating nsPropmpter error.

The thing is, the entire operating system becomes unusable. COMPLETELY UNUSABLE! Cairo (GLX Dock) CPU meter slams to the hilt, the mouse is unresponsive, and the hard drive LED stays constantly lit.

This can go on for 5 to 10 minutes. Sometimes it takes 5 minutes for the window to pop up asking to stop the script. The entire operating system is unusable at this point.

Why is a browser script slamming my hard drive like that? A browser script should not be hitting the hard drive.

This is a very serious issue that Ubuntu needs to address with Firefox. It renders the entire operating unusable.

$ locate XPCOMUtils.jsm

I have a dual-boot with Ubuntu 12.04 and Win XP. They are on separate hard drives. I don't use XP anymore unless absolutely necessary. However, fstab loads those Windows partitions on Ubuntu startup.

How is Firefox or a possible Firefox plugin running on Ubuntu accessing the Windows partitions on a separate drive?

Quite peculiar. What plugin would decide to install itself using Wine and on a completely separate drive?

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I suspect this is a problem with either Adobe Flashplayer, or whatever Java plugin you are using. Try disabling them one at a time and see if the problem goes away. – adempewolff Aug 23 '12 at 5:22
Of course the script itself isn't likely "hitting" the hard drive. Probably the script is causing the operating system to page a bunch of memory. – Nathan Osman Aug 23 '12 at 5:57
Agreed that the issue is serious, but without discovering its cause, I doubt if anything can be done about it. And it looks like not many experience this issue, so the culprit most likely is a plugin, or a userscript, or something like that, installed on your system. – Mahesh Aug 23 '12 at 8:59
Looks like this module has been nasty, from googling the name xpcomutils. here is something that may help You may consider trying mozilla support, but from what I see in the few posts I browsed, the activity on support forums seemed low. – Mahesh Aug 23 '12 at 9:20
Try unmounting the XP partition, and then running firefox. – green Aug 24 '12 at 9:16

Due to the complexity of the situation, I can't give a direct answer, but I can offer ideas on finding the solution to your problem.

  • Unless specifically instructed, it is Very Unlikely that firefox is accessing any Windows partitions. Just because the following file has the same name, that doesn't mean it is the file firefox is accessing. You can prove to yourself that firefox is not accessing the file you located by renaming it to XPCOMUtils.jsm.bak. Firefox renames a lot of its files locally, and will report to you the filename the server uses, even if it doesn't store it under that same name locally.
  • A script may be consuming a large amount of memory, and can cause your system to run out of physical memory and access swap memory. This will cause the system to slow down and access the harddrive. Otherwise, an internet script is not allowed to access your harddrive unless you specifically allow it.
  • Disable all your firefox extensions to eliminate them as a possible cause.

Try to find out which specific website(s) the problem is occurring on.

If the problem goes away after disabling your extensions, then it is likely that one of your extensions is at least partially responsible for the problem. Re-enable them one at time to try to discover which it may be. Some extensions take a lot of memory, so this too could contribute to the harddrive accesses.

If you continue to have problems after disabling your extensions, then your extensions are likely not the problem. It may be any of the following:

  • a bug in a plugin (like flash/java)
  • a bug in firefox
  • an intentionally malicious website trying to affect your machine
  • other?
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