Uninstall and then reinstall the burning software - try just installing one of them at a time at first and then run to check.If it's ok them load second.
When I had pinnacle on my old machine I just used that and it was fine, didn't load nero as I think there was some compatability problems with earlier versions of Nero v Pinnacle.
Try copying tracks to the HDD and burning from there (just in case you are trying cd to cd) you should then have no buffer under runs.
Apart from that try different media ?
I know it's a bit vague but I have been through the mill with mine and had to compromise.
I have a similar problem where nero copies CD's ok but the software that came with PC won't - but burns DVd's ok. Tried lots of things in the end I use nero for CD's and INTERVIDEO for DVD's .....