asterisk users - Apr 2006 - sip hang channels

Dear all,

we have problem with hang sip channels when lot of incoming calls to 
registered users. we are using SVN 1.2 16771 version.

xxx.xxx.xxx.xxx   639489919160  14aea9430d0  00102/00000  unkn  No       
Tx: CANCEL    
xxx.xxx.xxx.xxx   639485949581  1b3dd036127  00102/00000  unkn  No       
Tx: CANCEL    
xxx.xxx.xxx.xxx   639484589314  12f8b0fb4d6  00102/00000  unkn  No       
Tx: CANCEL    
xxx.xxx.xxx.xxx   639484131558  386850c668e  00102/00000  unkn  No       
Tx: CANCEL    
xxx.xxx.xxx.xxx   639482001240  466700fe087  00102/00000  unkn  No       
Tx: CANCEL    
xxx.xxx.xxx.xxx   639487637376  3aeedb022ef  00102/00000  unkn  No       
Tx: CANCEL       
xxx.xxx.xxx.xxx   639482001248  02f859b8511  00102/00000  unkn  No       
Tx: CANCEL    
xxx.xxx.xxx.xxx   639483957822  307a0bd50a5  00102/00000  unkn  No       
Tx: CANCEL

thanks

Ray