Sometimes when i try to transfer a relatively large PDF (20-50+ MB) i get this error: "Parameter incorrect".

It only happens when i try to transfer the file into iLiad's memory. there's enough space, i tried taking out the spaces from the title...still doesnt work.
I've put a file like this before (from school), and it worked fine.

Do you use the iRex supplied usb cable or your own? Just an idea.

I use my own (camera) cable because the supplied one does not work properly.

It might not be the cable, it might be the hub. My work around for a bad hub was to carefully position to remove all pressure from the hub's connector and then wrap the cable around the hub to hold it in place.

It was not the cable or hub, it was the iLiad's internal memory. Somebody from iRex told me in the forums to format the internal memory.

It did the trick, works great now.