I just wanted to say thanks to everyone who posted advice here - this thread just saved my bacon.
My R4 and Japanese Kingston have both been perfect ever since I got them.
That was until about 630 this morning.
I plugged the reader into my main pc and out of habit backed up the saves [thank heavens].
Then I copied a few games to it - Eye training, children of mana.
All seemed fine as usual.
Then when I tried to load Eye training [it was the American version] the R4 froze on the creating sav screen the green bar stopped moving. I left it for a while, no dice. Then tried resetting, no luck. So I turned off and on , R4 got to the loading screen then crashed. Next time it didnt get that far.
Put the card back in the pc with the aim of formatting, got the message "please insert disc".
Tried it on the wifes tower and both of our laptops, got the same bloody message.
Tried formatting it in a camcorder, no good. Tried her mobile, which at first didnt like it, then it formatted it into 2 partitions a gig each.
Connected it with a different reader with the big black SD adaptor seen on Striderx's image, and windows kept reading it again and again no luck.
Put it in the original R4 reader, was recognised right away with the mobiles directory inside saying it was 1 gig.
Used the SDformatter program which wiped it and resized it.
Took a long breath, not expecting much and the format worked!
Copied the latest R4 firmware, all of my saves and all the games I'm currently playing... and
Its all back to normal!
Will be buying a decent branded reader next week in TCR that's for sure!
So, erm just wanted to vouch for the advice given here, definitely worked for me and I really appreciate finding out here how to sort this headache out!