Asterisk 1.4.18.1 memory leak?

Memory leak with asterisk ?

I noticed this morning that almost all my memory was used (2gb !) I stopped the asterisk services and misdn services but the memory was still the same. Only after a reboot of the system did i have 1700mb memory free. But now I notice that it is slow climbing down to less memory . It goes about 1 mb per 10 minutes but it will not release this amount of memory anymore. So in a few more days my memory will be full again .
It does not take any swap memory and its measured with the free -m

Linux version Red Hat 4.1.2-14

[root@vcitamil001 asterisk]# asterisk -r

Asterisk 1.4.18.1, Copyright (C) 1999 - 2008 Digium, Inc. and others.

Created by Mark Spencer <markster@digium.com>

Asterisk comes with ABSOLUTELY NO WARRANTY; type 'core show warranty' for details.

This is free software, with components licensed under the GNU General Public

License version 2 and other licenses; you are welcome to redistribute it under

certain conditions. Type 'core show license' for details.

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Connected to Asterisk 1.4.18.1 currently running on vcitamil001 (pid = 3120)

Verbosity is at least 3

vcitamil001*CLI>