The summary, approximately: there are some crashes detected by Firefox and it seems Firefox (or whatever Firefox uses as its libraries) thinks it can use AVX instructions even if the OS isn't aware of the AVX technology and therefore can't preserve the content of the registers during its "normal work."

And yuhong has found that the reason Firefox thinks that, specifically on Windows XP which is booted with the Windows 10 loader, is that the Windows 10 loader sets some bit "I know about AVX" instead of clearing it before entering in Windows XP.