Sorry, I've deleted and reinstalled clrmame several times because I feared that the problem was caused by some options, but the problem is present also with default settings after a clean install (or decompression, I use clrmame zipped version). The dat is the latest nds no-intro set (2008-07-29 15:44:02), not numbered, encrypted, no unlicensed, no bios.
http://datomatic.no-intro.org/?page=download
For the rom, i think it doesn't matter. I renamed on purpose old roms with wrong names and the error appears every time, with other dats and romsets as well (n64 for example).