Breaking derailleur hangers on NRS

I have a 2001 Giant XTC3 NRS. The derailleur hanger has snapped 6-7 times over the time I have had it and its happening more often lately. When it's healthy its a great ride but its not reliable It seems to go when I do small jumps. The chain lenghth is right, and I have changed the rear cluster, derailleur, chain rings and chain since the problem started. Has anyone had this problem. One suggestion is to replace hanger with stronger one. I'm worried that I'll damage the frame or derailleur. Local bike mechanics are also baffled.
Cheers from NZ
Gunga

 

pm [email protected] at www.ridemonkey.com and see if he has any suggestions.