The default behavior is that tiny transactions cost more fees than "normal" transactions. And, to the extreme, any transaction with 0.1 or less bitcoin to be transferred will cost 0.1 bitcoin fee.
As you have less than 0.1 bitcoin in that wallet, you might be out of luck.
Normally I don't seem to pay fees on instawallet. Maybe they set it up to normally not need fees, but this special rule is still active?
Ente