USB thunbdrive de-initialized by Windows 10!

64GB USB (NTFS) thumbdrive - worked fine until I stuck it in a 'new' Win10 machine - the drive then came up as uninitialized
Thought I must have removed it from the last machine without ejecting properly, so reinitialized and reformatted as NTFS on my WIn7 machine and loaded it with 6+GB of stuff for transfer...
Stuck it back in the WIn10 machine and it was de-initialized again.

This time, I Initialized and formatted it in Win10 (as exFAT) - put it in the Win7 machine and it was OK - put it back in the Win10 machine, and it was still OK.
Now putting the 6GB data back on it for transfer to the Win10 machine - with fingers crossed!

Anyone know what's happening here?? - and WHY??


edit - Just put the stick back in the Win10 machine - and it got trashed AGAIN!!

Problem solved - it was the dregs of the pre-installed McAfee!!

Ran MCPR and everything worked fine.