Romcenter

Yes, in mame xml:
with crc -> baddump
without crc -> nodump

Hmmm. Ok, scratch that. I found out what happens. It seems that (in mame 0.163 at least) there are same games with bad dumps that HAVE a CRC and some others that DO NOT HAVE a CRC. RC cannot fix the ones having a CRC, which seems logical. Perhaps this should be mentioned in the log file (i.e. cannot create dummy rom <NAME> because it has a CRC).

I have a game which is yellow. It contains some proper, some badly named and some missing/corrupted roms. Selecting Fix\Create dummies should create the missing/corrupted roms, but in this case it does nothing. This option only works if the game zip contains only green roms and red missing/corrupted ones. If at least one yellow rom exists in it, Fix\Create dummies does nothing.

To be honest, i'm not 100% sure this is the case. Fix\Create dummies sometimes works and sometimes it doesn't, but from what i've seen in my tests, it seems to depend on whether the game contains yellow roms or not (or perhaps other missing but not corrupted ones).