Some people have misgivings about what Google does, but it is unlikely any add-on you download is going to be malicious if it is a main Google site. * What is the add on ? (or the link that it shows) ? *Check you have javascript enabled, and look at your add-ons to see if any of them are disabled. *What is the actual site that is offering ann addon ? I just hope you do not already have malware that may be re-directing you somewhere else. I am also worried if you say the computer crashes. If you have crashes please post a couple of the CrashID s I suggest you also scan for malware with updated tools.You may find it best to download such tools on another computer, just incase that is also re-directing or blocked. ----------- CRASHES Please perform the following steps to give us a crash report ID that helps us find out more about the cause of the crash. #Enter about:crashes in the Firefox location bar (that's where you enter your website names) and press Enter. You should now see a list of submitted crash reports. #Copy the most recent 2 report IDs that you see in the crash report window and paste them into your forum response. More information and further troubleshooting steps can be found in the [[Firefox crashes]] article. -------- MALWARE Sometimes a problem with Firefox may be a result of malware installed on your computer, that you may not be aware of. You can try these free programs to scan for malware, which work with your existing antivirus software: * [http://www.microsoft.com/security/scanner/default.aspx Microsoft Safety Scanner] * [http://www.malwarebytes.org/products/malwarebytes_free/ MalwareBytes' Anti-Malware] * [http://support.kaspersky.com/faq/?qid=208283363 TDSSKiller - AntiRootkit Utility] [http://windows.microsoft.com/MSE Microsoft Security Essentials] is a good permanent antivirus for Windows 7/Vista/XP if you don't already have one. Further information can be found in the [[Troubleshoot Firefox issues caused by malware]] article. Did this fix your problems? Please report back to us!