I don't know if this is exactly the same problem, but here's what happened to me:

One day when I opened Firefox I got a prompt for updates. I got upgraded to version 3.6.16. That was over a week ago. This morning, I opened Firefox, got a prompt for updates, clicked ok, and I ended up upgrading again to 3.6.16. Norton gave me a notification about some file being used by fewer than 100 people and having "medium risk", but I wasn't able to take any action, just read.

Once that upgrade went through every time I tried to open Firefox, it'd pop up, I'd click no to "Do you want Firefox to be your default browser" and then it'd go white and freeze up. I'd get a message from Windows that there's a problem, Firefox has stopped working, it will be closed. No information was sent regarding the problem.

When I'd open Firefox I'd see two tabs: one about the upgrade to 3.16.6 along with an invitation to upgrade to version 4, and another being my homepage to yahoo.com.

I also have Internet Explorer, so I opened that, went to Firefox's website and downloaded version 4. So far that has taken care of the problem~I can use Firefox again.

However, I did have a couple small difficulties while downloading version 4. Right off it would not immediately start running. That was blocked by my Norton. So I had to click on "click here". Also during the process I got a message about two add-ons being incompatible, so they were disabled, and no updates could be found. They were: Microsoft .NET Framework Assistant 1.2.1. and Norton Toolbar 4.6.

I worried it was a virus but it seems like more of a compatibility problem involving maybe Norton? I have the 2010 version and haven't upgraded to Norton 2011 yet.

Anyway, like I said, so far version 4 is working fine, but I thought I'd pass on the incident.

If Norton is preventing plugin-container.exe from running then that can very well cause firefox to stop working properly or even crash.

Unfortunately there isn't much we or you can do until Norton updates and starts supporting Firefox 4. They have known that Firefox 4 was going to be released for a long time so hopefully they are working on enabling Firefox 4 already.

get rid of norton guys its obviously causeing an issue..but not the main one. its just complicating issues here. next. ive got the sme problem. after 3.1.16 installed.. it stopped working properly keeps closing out and stuff . so not sur4e whats causing it yet . as soon as i find out i'l let you guys know