Let's take for example espnsped, in the dat, for the parent set it's:
<game name="espnsped">
<description>ESPN Speedworld (USA)</description>
<year>1994</year>
<manufacturer>Sony Imagesoft</manufacturer>
<rom name="espn speed world (usa).bin" size="2097152" crc="f50be478"/>
<driver status="good"/>
</game>
for the clone (the prototype game), it's:
<game name="espnspedp" cloneof="espnsped" romof="espnsped">
<description>ESPN Speedworld (USA, Prototype)</description>
<year>1994</year>
<manufacturer>Sony Imagesoft</manufacturer>
<rom name="u4.bin" size="524288" crc="525788b1"/>
<rom name="u5.bin" size="524288" crc="ada9c9a8"/>
<rom name="u1.bin" size="524288" crc="e8ee1029"/>
<rom name="u2.bin" size="524288" crc="0f3ec491"/>
<driver status="good"/>
</game>
does the issue go away if you put the prototype set (espnspedp) in? I think it's complaining about the clone being gone for a merged-set.
best regards,
- dink