Memory usage on debian etch

[devnulled]

Hello, everytime i restart this box the memory usage goes up every minute according to top, until it uses 36K of swap and then stops.
I can't see the process that uses the memory, check this out

$ ps aux | awk '{print $5}' > mem
$ b=0;for a in `cat mem`; do b=`expr $b + $a` ; done;echo $b
expr: non-numeric argument # because the first line is VSZ
516596

So that's around 512MB. I have 1GB ram and when I run top I see this

Mem:   1027412k total,   996588k used,    30824k free,   154012k buffers
Swap:  2650684k total,       36k used,  2650648k free,   744516k cached

I've never seen this before, any ideas? The kernel is 2.6.18-5-686, the processor is core duo 2 T5500 if that helps.
I tried restarting, all my processes at start up run, mysql, courier, apache, proftpd, sshd etc and their memory usage isn't changing at all. But in few hours suddenly I've used up all my memory and the box starts to swap.
Thank you.
Before you jump to a conclusion that my box might be compromised, this box doesn't have access on the internet, it's deep inside my LAN.

[Coburn64]

May I ask what platform you're using and what GUI are you using?

Eg. x86_64 and KDE 3.5.x ?

[sathiya]

I can't see the process that uses the memory,
why can't, put top, and press M, to see the process which accesses much memory...

And, i think no problem because most of it are cache....

Any more clarification ?