[Serusers] Voice problem

Hi all I have installed CDROUTER working fine for 30days now almost all iam able to see 120 users calling at a time no problem but past 7days iam getting lot of voice breaking problems and other side not able to hear my side voice my Server config Xeon with 1 GB Ram 86GB hdd and most of the time looks like below ~# free total used free shared buffers cached Mem: 903484 897328 6156 0 1892 830208 -/+ buffers/cache: 65228 838256 Swap: 0 0 0 when i check top Cpu use is 2% only when i configure directly with provider using PAP2 , voice is clear can some one guide me what is the problem how can i test and how can i resolve this problem help will be appriciate Ram