If you are using McAfee, please contact their product support line. I have seen messages here today where they have modified setting to fix slowness issues.

We did modify our McAfee settings but I'll try them again. I'm not sure, though, why running McAfee in the background would cause Thunderbird to freeze up and give me a "Not Responding" message after the email has already been downloaded into my inbox. I get that message when I'm trying to delete an email that I may have already read and responded to.

Simple really, it is not in the background, it is in there hammering away. McAfee are scanning the actual file Thunderbird is trying to read. Bit like sharing the Sunday paper with your wife. You can do it, but it is not optimal and you fight over the cartoon page.

I have this problem too and it is EXTREMELY frustrating!!!

@Jennis, what are you posting here for. Contact McAfee, It is not a Thunderbird issue.

I had this problem, also. It was a McAfee problem for me, too. I have McAfee Total Protection. The fix was to open my McAfee interface, go to the Virus and Spyware Protection, click on the "Schedule and Run Scans", then on "Real-Time Scanning". I left it turned on, but clicked on "Settings" and then scrolled down to "Boost my protection" and unclicked the "Use Active Protection for live defense against threats". The problem is no longer occurring.

I have the same problem and I do not have McAfee. Repeatedly when I try to delete an email or move or it mark it I get the Thunderbird not responding message and have to exit the program (with Ctrl Alt Dele) to do anything. It is very frustrating. I put it in safe mode but that did not fix the problem.

I think it is a thunderbird issue because I constantly get that message and I do not have McAfee on my computer.

JanSw, why not just post your actual problem in your own thread instead of trolling old posts that have nothing to do with you? You might actually get an answer to YOUR problem.

I do not have McAfee, I have Webroot SecureAnywhere v8.0.4.123, (the foreground window is protected by Identity Shield) installed on my computer and have had the entire time I've had Thunderbird with no problems until now. I haven't changed any settings or made any updates. It has always worked fine until last night when I logged on. It will open, however if I click anywhere on the page it turns grey and immediately freezes. I receive a 'Thunderbird is not-responding' message.

The original poster to this thread found their solution, and they continue to be spammed as do I with others posting their only vaguely related issues. So, I am going to lock this thread to prevent further posting here.

If you have an issue post a question of your own on a new thread.

In an effort to help and to save time and get people moving. anyone with issues needs to make themselves familiar with the following.

Anti Virus issues from the Wiki If you see not responding or constant grey outs. I do not care what anti virus you use. They update at least daily and are the number one cause of performance and connectivity issues. We note (or try to) current issues on the Wiki, but seriously we rarely get information so it comes back to the volunteer testers to identify most issues. To handle diagnosis of this type of issue, starting the operating system in Safe Mode with Networking often works and points straight to the anti virus (which windows does not load in safe mode)

The second most common solution is an add-on that did not get a needed update following a Thunderbird update (so they are in conflict). Restarting Thunderbird in its own Safe Mode (that is with add-ons disabled from the help menu) will automatically clear the issue and leave you the process of working out which is the cause as you re-enable them one by one.

The following is a standard response to this type of issue. Everyone should try the process before making a post, as someone will only ask you to do it in another way, or offer the information verbatim.

To diagnose problems with Thunderbird, try one of the following:

• Restart Thunderbird with add-ons disabled (Thunderbird Safe Mode). On the Help menu, click on "Restart with Add-ons Disabled". If Thunderbird works like normal, there is an Add-on or Theme interfering with normal operations. You will need to re-enable add-ons one at a time until you locate the offender.
• Restart the operating system in safe mode with Networking. This loads only the very basics needed to start your computer while enabling an Internet connection. Click on your operating system for instructions on how to start in safe mode: Windows 8, Windows 7, Windows Vista, Windows XP, OSX

If safe mode for the operating system fixes the issue, there's other software in your computer that's causing problems. Possibilities include but not limited to: AV scanning, virus/malware, background downloads such as program updates.