asterisk users - Dec 2007 - Cannot allocate memory

Hello,

I have a problem with our asterisk server. (Version 1.4.15 RPM Build running on
Fedora Core 7)

After 3 day's running, i'v got this message in my logfile:
Dec 14 13:14:09 amsec-tk1 asterisk[4321]: VERBOSE[11363]: -- Executing [9020 at
AMS-UPPORT-HOTLINE:1] System("SIP/SN2400-67ec6aa0", "echo -e
"Eingehender Support Anruf am 14.12.2007 um 13:14 durch die Nummer
<06xxxxxxxx> \n" >> /drbd/ams-support-hotline.txt") in new
stack
Dec 14 13:14:09 amsec-tk1 asterisk[4321]: WARNING[11363]: asterisk.c:820 in
ast_safe_system: Fork failed: Cannot allocate memory


Reserved memory was about 1,5GB of RAM!
After restarting Asterisk, the system is normally running until yet.

Is there a memory leak in this version?

thanks for answer
Thomas