hello dave, other users with this problem all had an embedded intel hd graphics card with an old driver present. in case this also applies to you, here would be a link to update the driver, which in turn should also address the black firefox problem. * Intel HD 2000/3000: https://downloadcenter.intel.com/Detail_Desc.aspx?DwnldID=23764 (for win7 64bit) * Intel HD 4000: https://downloadcenter.intel.com/Detail_Desc.aspx?DwnldID=24329 (for win7 64bit) ^{[http://www.intel.com/support/graphics/sb/cs-009482.htm Intel guide to find out which model you're using]} in case this doesn't solve the issue or does not apply to your system, start firefox into safemode '''by pressing the shift key while the application is launching''' & disable hardware acceleration in the firefox ''menu ≡ > options > advanced > general'' (that setting will take a restart of the browser to take effect). [[Troubleshoot extensions, themes and hardware acceleration issues to solve common Firefox problems]]

Starting Firefox in Safe mode and disabling hardware acceleration seems to have done the job. Thanks for your help.