Precise faults

[Roger]

We use Precise here at home on desktop and laptop.
Desktop has 2 gig ram, is 2 years old, laptop new Toshiba, 8 gig ram.
We are finding that the system slowing and faulting more frequently 
since the last 3 Precise kernel updates. I am wondering if there is a 
kernel fault.
As an aside, I have noticed that after the latest kernel update in 
Fedora 16 it too stops more frequently.

The screen goes dull, nothing works, can't use mouse or keyboard for 
minute or so then all good for a while, until the next fault.
It happens with Firefox, Gimp, Libreoffice, Inkscape.
There's nothing I can find in /var/log and top just shows the delay time.
I have run apt-get autoclean.

It is quite frustrating for me working on a remote server with Drupal 7 
and the system stops mid sentence for a minute or 90 seconds as I am 
modifying a field. Sometimes I just have to reboot to get the machine 
running again. This does not happen with Fedora 16 on the same pc. So it 
seems to be a Ubuntu issue in this instance.

My 2 gig memory runs at between 40 and 60%, My daughter's Toshiba at 10-12%.

My daughter and her Toshiba laptop had continuous stops and reboots 
yesterday after the latest updates.

This did not happen before so I'm not sure how to tackle this or where 
to look for causes.
Help is greatly appreciated
Thanks
Roger