Burning a data DVD Problems

While trying to burn data from an external HD to DVD+R using Nero burning rom, it said “burn successful” but my drive couldnt see it, but when i tried to continue the multi-burn session, nero “saw” the files but would,nt high light the sessions so i could not carry on the burn. the DVD+R are now coasters, as i can not do anything with them.
I cant think where i went wrong.The only clue i have is that the files to be burned had two folders included which appeared on the far left,of the burning rom page under the new disc symbol on their own. Did these folders confuse the multisession burn process?
When i left out the two folders , all went well.
Can anyone throw some light on this problem? Thanks in advance…