Failed Wireless Transfers

Hi

I have D-link DI-524 router and I want to transfer big files (> 2Mb or more)
to another machine, I talking about wireless tranfer but not having much
luck, small files seems to transfer ok (< 1 Mb), transfers seems to drop
most of times on big files doesn't complete a whole file. I tried moving the
antenna & also tried moving router different location but I get the same
results (70-75%), the distance of one machine to another is not even 100m.
Router & PC Card are the same brand, PC Card is G+ version.

Sal