First, try to reset Firefox. Refresh Firefox - reset add-ons and settings. This simple step will eliminate many Firefox problems with only one click.

A few other basic trouble shooting things you can try is this: Run all Windows Updates, install all needed service packs, etc.

Update your graphics driver (Firefox uses your graphics card for some rendering, and an out of date graphics card driver can cause problems. Upgrade your graphics drivers to use hardware acceleration and WebGL

Update all your plugins (Flash, Java, etc.): http://www.mozilla.org/plugincheck/.

Download and Install MalwareBytes Anti-Malware, run a full Scan. http://www.malwarebytes.org/. This helps check that there are no viruses on your computer causing issues. You can uninstall this program after you clean off any infections.

See also: Problematic Extensions

Hmm. It seems to be fixed. I'm not sure what did the trick. I disabled the Flash plug-in (11.3.300) and reinstalled the ATI video drivers. Thanks for the support, -- Jon

Your problem sounds like the one that a co-worker and I started to have about the same time. Check your Symantec client management control log. You might see a line like the following.

Date and Time Severity Level Action Test / Production Description API Class Rule Caller Process ID Caller Process Parameter User

2012-07-30 10:48:09 AM 15 Block Production Unauthorized NT call rejected by protection driver. System Built-in rule 1608 FlashplayerPlu FuncID-B6H, R... None

At first we thought that it was a Javascript problem until we noticed this log. The key words are 'Block' and 'FlashPlayerPlu'. This problem recently started for us, perhaps with a software push 1-2 weeks ago. Internet Explorer does not hang when accessing pages with Flash.

The Flash page does eventually load after a long time. However, since the whole browser hangs for a while, for the most part having the Flash plugin enabled makes Firefox unusable if accessing pages with Flash.

Disabling the Flash plugin solves the hanging problem, but I do not know what is causing the problem, nor do I know when a combination of Windows 7, Flash, and Symantec will work. Your later version of Symantec shows that we might have the problem for a while, but I do not know what customization CSC did with Symantec. My coworker did run a complete virus scan, uncovering nothing. Another co-worker is running Windows XP. She does not have the problem, but I do not know what other versions of software she is running.

Symantec Endpoint Protection version 11.0.6100.645

Flash version 11.3.300.268

Firefox version 14.0.1

Windows 7 32-bit service pack 1

The control log also showed blocks of the AcroRd32.exe process. Ever since the push of Adobe Reader X onto my machine earlier this year, deleting or moving .pdf files has caused a long hang, such as before the deletion confirmation popup appears. The hanging was proportional to the size of the file, as if a security scan was being done. Using key words from this problem, I found the following 2-year old link. It mentions a 2-year old registry edit workaround between Chrome sandbox and Symantec conflicts. It also refers to SysPlant, a term I have seen while researching this problem.

http://www.symantec.com/connect/forums/google-chrome

SysPlant reverted from 4 to 1 after resetting, so I had wondered whether anything had happened. However, both issues seem to have disappeared. I do not have any idea if I put security of my machine in jeopardy, but at least it is more usable.

Hi nocscsupport,

Thanks for the detailed feedback. It would also be helpful if you could report it here. They may be able to work this out with Symantec.

There could also be another safe way to allow trusted processes in Symantec Endpoint Protection and prevent silent denials. The Symantec support would most likely have helpful pointers in this regard.