[Serusers] ERROR: nathelper::timer: out of memory

Hi, maybe someone can help me with this Problem. Actually we have 300 Users in our location table, having nat_flag = 4; Servermemory: total used free shared buffers cached Mem: 1029208 971552 57656 0 115460 572440 -/+ buffers/cache: 283652 745556 Swap: 996020 6300 989720 System: Debian 2.4.24 Ser: sip_router_0.8.12_stable # -- nat Params modparam("nathelper", "natping_interval" , 20) modparam("registrar", "nat_flag", 4) every 20 Seconds I have the Error in SYSLOG: ERROR: nathelper::timer: out of memory I found the Error message in the ser/modules/nathelper.c code but i am not really a c programmer. any ideas? Best Regards, Markus