Hello FrancF, Thank you for posting on Mozilla Support. We value and appreciate you as a user. Please do a malware check on both computers. 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 some of the following programs to scan for malware: * [http://www.microsoft.com/security/scanner/default.aspx Microsoft Safety Scanner] * [http://www.malwarebytes.org/mbam.php MalwareBytes' Anti-Malware] * [http://support.kaspersky.com/faq/?qid=208283363 TDSSKiller - AntiRootkit Utility] * [http://windows.microsoft.com/MSE Microsoft Security Essentials] (A good permanent anti-virus 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! ---- Did you know that Mozilla Support is helped out by volunteers? Be part of SUMO! http://mzl.la/OJtpch Donate more than $30 and get a T-Shirt! https://donate.mozilla.org/page/contribute/joinmozilla

Opt-out of HTML5 video on YouTube. * [http://www.youtube.com/html5/] * [https://bugzilla.mozilla.org/show_bug.cgi?id=775491] - HTML5 unresponsive script errors on YouTube * '''''(Please do not comment on bug reports)'''''

Scanned for Mal ware- 0 found, Scanned for virus's -0 found. Once I reinstalled FF 18 all was good, The second you shut it down It reverts to the same problem.