Maybe I found the cause (at least some of them). Here below some cases:
Files listes as NULL (characters componing file name):
-.'029aAcDehimMnoPrRsUvx
_-,.()169abcCeiJlLmnoPrstv
-.'()#125aAbcdDefgiIlmMnoPrstTuUvx
-.058aAceÈFiLmMnPrstUvx
_-,.#0269abBcCdefgiJklLmoOPrstvWy
-.'()#125aAbcdDefgiIlmMnoPrstTuUvx
_-,.#01238abBcdefFgiJklLmoOpPrtTvy
-.15acdeilmnoprtTuUvx
-.157aAbcCeiLmMnopPrUvx
-.()&012349aAbCdDeEGHiJklLmMnopPrRstvwy
-.'()#025aAcdDefilLmMnopPrstTuUvx
Files listes as "N/A" (characters componing file name):
-.'()#125aAbcdDefgiIlmMnoPrstTuUvx
-.()#015aAcdDefiIlmMnoPrtTuUvx
-.()&012349aAbCdDeEGHiJklLmMnopPrRstvwy
Conclusion: seems that this error is generated by some chars, as # or & ' , or accented letter, as È .
Don't know if this behaviour is changed in last CVS version, since I'm still using 20060504 one.
Cheers,
Sandro