@Pink Tissue
I have tried nearly a dozen brands in my original foray to try to find one to act as my main flash updater card, including those you mentioned.
The ones I found best were the cheaper brands - FujiFilm & Silicon Power were the only ones I could get to work properly for flashing firmware.
@Tirwal & Pink Tissue
Also tried bigger cards 8gb - seems to only work if I keep the data on them under about 3.5gb - if I go over this the card becomes unstable.
It may have been the original out of date firmware - I'll give it a try over the next few days on couple of different 8gb cards I have left and see if it works any better.
My complete library is about 7gb of Tech manuals, Fiction & Non fiction, help files and other documents - all in NON-DRM PDF or ePub and scattered over about 3 or 4 cards of 4gb capacity. If I could get then all on one 8gb or 16gb, that would be perfect
If I get any satisfactory results, I'll post back here.
Thanks for your comments.