system crashes after each stand by

Hi all,
recently (for the last couple of weeks) the my system freezes when I try to put it in stand by (or if it goes due to inactivity) - not sure why this is happening - I have installed 11.4 a few months ago and never had any issues -
any ideas on why this is happening?
here is my system details:
Acer N53J (i7-74QM), Opensuse 11.4, Kernel 2.6.37.6-0.9-desktop, Gnome 2.32.1