As Cfitz said before, giving the exact error message + version would be very helpful.
In ISO Tab, also select "Max of 31 Chars (ISO Level 2)" along with other settings suggested. You only need to select this once, and after a successful burn and Nero will remember it thereafter.
Btw, what is original length of your filenames?
HTH / Good Luck
Stone walls do not a prison make,
Nor iron bars a cage;
Minds innocent and quiet take
That for an hermitage;
If I have freedom in my love,
And in my soul am free,
Angels alone that soar above
Enjoy such liberty. - Richard Lovelace