Not enough space error - but there is

[Reverend]

I created a partition of 931 MB, then tried to copy stuff to it. I get 'Not enough space.'

If I choose a 3 gig file, the error says 'You need another 3 gig to complete the operation'

If I choose 50 gig, the error says 'You need another 50 gig'

How do I fix it?

Thanks - rev