USB Hub Problem

This is really weird. I have two USB connectors on the front of my computer but because they are close together, I can't have two usb leads in together because of the space in between. So I use a USB hub with four connectors on it. When I plugged my memory card into it, I got a message saying it was full, and and then another message saying that there was an error and that all data had been wiped!. When I then plugged the USB lead in direct (not via the hub), it performed normally. Can anyone explain this anomaly please. The fact that it's used via a hub shouldn't make any difference, should it?

Some USB devices just don't work well with hubs.

USB devices need to draw power via the USB port on the pc.

USB ports on the pc have only so much power to give out.

Some USB devices need more power then others.

I usually buy A/C powered hub for this exact reason.