ATV1 USB Drive file size limit

I have an ATV1 with firecore and since the death of a Mac we connected a 3 TB USB drive formatted HFS+ (? - some mac format anyway). That disk is shared via SMB to Linux and Windows machines. The problem is at least confirmed consistently when writing files from a Linux Mint 10 (ubuntu 10.10) client, we can not copy files larger than about 590 Meg to this connected USB drive from the network. This was confirmed via two different Linux Mint 10 Machines on the network.

 

 

This does not happen on the FAT32 USB disk

 

Any idea what may be the cause or a fix?