Squeeze: problem after installation on laptop

[Stanislav Gudkov <gustas88@gmail.com>]

Hi

I've installed Debian Squeeze on my Acer Aspire 5536G and discovered
some functions doesn't work correctly.

Here's a list of non-working things:
1. Fn + arrow Up (to make sound louder)
2. Fn + arrow Down (to make sound quieter)
3. Fn + F8 (mute)

* now I can only change sound level in alsamixer.

Another Fn + [...] functions work normally.

Package 'acpi-support' is installed.

Please, help me to decide this problem cause thematical forums keeping
silence and I don't know what to do.
___________
Regards
Stanislav