I'm using ubuntu 11.10 (ubuntu's recommended Radeon VGA driver is error) on my HP 431 (CPU Intel core i5 2410M - 2G Ram - 320 HDD - Radeon HD6470 VGA). Everything is OK, except heat problems (it's not happen on Win7). Is my HP 431 (Win7 pre-setup) can't use ubuntu? Sorry my bad english.
Problem can be caused by many factors. At first I suggest to check currently running processes and check if any of them is not consuming your whole CPU resources:
If you'll find some suspicious process, you can try kill it by typing kill -s KILL process_id in terminal window (process_id is listed in the 1st column at previous used 'top' command).
I was facing a similar problem on my Hp 431-452TX (i5, 4gb, 6470m-1gb, win7 x64U, Ubuntu 11.10), but there was a variation, i am running Ubuntu 11.10 (upgraded from 10.4) x64 and Win 7 Ultimate x64 on seperate partitions, ubuntu was running cool, but Win7 was heating the CPU badly, I had core temp installed in windows which hibernated the system when the CPU was over th 85 degree Celisius mark. and the system was regularly shutting down even after using a Cooler Master cooling pad.
First I learnt that the machine was susceptible to dust, and litreally i blew out tons of dirt from the blocked vents, it worked right till a week and started again, blewing out was not an option, then,
I just learnt that the BIOS was updated to a newer version F.24 on Oct 7, 2011 (check here http://h20000.www2.hp.com/bizsupport/TechSupport/SoftwareIndex.jsp?lang=en&cc=th&prodNameId=5086746&prodTypeId=321957&prodSeriesId=5086745&swLang=13&taskId=135&swEnvOID=4061#93211), just updated it 20 minutes ago, and I think this has done the trick
I hope it works for you!... All the Best!