Thanks for coming back.
I avoided FF 6.0.2 as many of the Add-on I use are not compatible with it.
I have checked drivers and they are all fine.
The PC is 'clean' I vacuum it once a year in the spring. I also use Everest Home for checking temperatures/fans etc. and they are all fine.
Will try flushing, it could possibly be that - I'll let you know.
AVG is V 9 - I couldn't get 2011 to install and think it likely 2012 will be the same :-))
I have had the same anti-malware for 5+ years so feel it unlikely that it may be this. Only one is active - Spyware Terminator - the others are used for scanning.
I have 106GB free space and only <1GB of RAM in use - 2GB installed.
HDD is relatively new and I am wary of running CHKDSK at the moment although it is only programs that freeze - I can (generally) use the remainder of the PC including other software.
I should add the only other thing I have found is a single entry in the Event Viewer (Applications) for database corruption in 'ESENT' - not sure what that is, am investigating.