Neo Dual Layer - burning

First of all sorry for my english.After months of burning data with a Neo dual layer suddenly it works no more.I am using as program Nero 6 with upgrade pack 1 and 2.Audio files are ok ( but not all the times)but when I try to burn divx or xvid as data files it is no more posible to have successful results.Errors are always different,from" invalid block address" to "could not perform end of disc at once".
I have tried to use the burner with others PC and it works properly, also with different kinds of DVD.Also tried to cancel Nero and re-install it but without results; simultion is ok but when I try to write it fails everytime.My computer is an Evo N1020V with Xp Pro SP2
2.4Mhz - Ram768.
Any suggestion will be helpful
Thanks - Simon -