John: put your handbag away
Let's deal with some myths & facts shall we.
(i) Firefox was a memory-hog until version 7, i.e. until a couple of weeks ago.
Actually John there have been no major changes to Firefox since Mozilla started their rolling release with Firefox 4 in the spring. Some previous versions of Firefox have suffered from memory leaks on both Windows and Linux but that has been much less of a problem since 3.5 - i.e. a long time ago.
(ii) Firefox has tendency to crash.
Well no actually, if you're judicious about the add-ons that you install it's very robust, even on Windows, has been for a very long time.
(iii) McAfee known for more reliable software than Mozilla.
My first instinct is to helplessly fall about laughing at this. McAfee almost ranks with Norton as a producer of "security" software that is only a notch or two above scareware in the way it tries to terrify lay users into unnecessarily forking out their hard-earned for peace of mind.
In fact Firefox plays nice with hundreds of different add-ons, including a pretty cool one called NoScript that helps to protect from malicious scripts and accidental clicks for free - you may have heard of it. So on balance who is likely to blame for this problem between Firefox and McAfee's ScriptScan? It's pretty obvious, unless you have some ***evidence*** to the contrary, John.
However I'd go further: I reckon most people who genuinely take an interest in the security and reliability of PCs, their own or those of others professionally (guilty!), couldn't give a flying fuck if it is Mozilla's fault in some way. To very badly paraphrase Winston Churchill: after the next update Firefox will still be a great browser, but McAfee will still be a steaming pile of donkey pooh for which there are many better alternatives (which don't have any problem at all playing nicely with Firefox).