this is one of the worst errors to crack (in my experience)
the reasons range from memory leaks, faulty hard disc , hardware and ram.
this isn't the whole reason ....
generally people don't realise how little memory 90% of software actually requires ... windows tends to keep files in memory until the space is needed ... so on the face of it all your ram is taken ... but not much is actually in use
so a few faulty locations right at the end of the stack don't matter
HOWEVER - with extremely hungry software (esp multimedia of all types) they need everything you can give .... so when you use them ... all of a sudden the few faulty locations DO matter
and you get this message ....
this is by no means the only reason ....
start by cleaning up your HDD -
http://www.ccleaner.com/download
run chkdisk and defrag
if no joy
try removing / reinstalling nero
I'd then start on the ram.
remove all the sticks ... and try them one at a time
then a pair ... then .... you get the idea
then run
http://www.memtest86.com/download.html
which will take ages (depending how much ram you have
even better d/l
http://www.ultimatebootcd.com/
and run each check in turn