This driver I was make against unstable Tiger using Leopard sources and Xcode 2.5 with Tiger universal binary frameworks

It helps me to have stable LAN connection

Many people use it in Leopard with success

Installation

1. Remove any AppleRTL8139Ethernet.kext from Your System
2. Remove file:///System/Library/Extensions.kextcache and file:///System/Library/Extensions.mkext
3. Copy attached kext into file:///System/Library/
4. Fix Disk Permission using Disk Utility (or type and execute    sudo chown -Rv root:wheel /System/Library/Extensions/*     in terminal)
5. Reboot and enjoy