If I understand this correctly, you used to have sucess and now you don't ? As time goes on, things get added that run in the background process.
If Nero doesn't solve your concerns, you could possibly try a few other things.
A defrag of your Hdd might help.
Some Hdd housekeeping as suggested in THIS post sometimes clears out some problems.
Running a program such as ENDITALL sheds lots of the unnecessary process that cause editing problems.
Copy the disc to a folder on your desktop, and rip the disc from there.
These are just some random ideas that I would probably try. 