Why does my wireless system give me problems when I add a second repeater?

I have a Bosslan 802.11g router transmitting my broadband signal and another similar device set to bridge to amplify the range. When I add a third device also set to bridge the system works for a while then breaks down,when I disconnect the third device it works again after a few minutes. It does not matter which repeater I connect, they both work on their own but not together. Curiously I didn't notice the problem until I set the devices to enhanced mode where it said: CCK Level: Default(18-19dbm) Enhanced(20-23dbm) Maximum(24-26dbm) I did this because I need some extra signal strength. The three devices are positioned in a triangle each about 60 meters apart with direct line of site (they boast a range of 400 meters) to provide my house and studio with internet, I live in a remote area without interference.