Generally as for flavortext.xml and gc2_conversations.xml... this is the xml schema(no records in it) for them...

MaxNumRacesInFile -- I think it defines the max limit for races w thin the file, 12 majorraces + generic + dreadlords(?) + pirates(?) , I have not tried to increase the value, it might not work anyway...
Topic name="xxx" -- its quite obvious, for what it is for, one record in the topic table(with FK topics)
Dialogue -- one record in dialog table(with FK topic)
Speaker name="xxx" -- who is speaking, I do not know for what the content integer values are for, but I guesss they are RaceIDs
Listener name="xxx" -- who is listening, same for int value here...
Phrase morality="0" -- the dialogtext for being good
Phrase morality="1" -- the dialogtext for being neutral
Phrase morality="2" -- the dialogtext for being evil
That's it 
Maybe Kryo can further specifiy the maxnumraces and the content values for speaker and listener?
He might even ask the devs, if he doesn't know? ^^
It'd be nice to know especially about the speaker/listener content value, since I'd know what the dropdownbox in my conversationseditor was showing 

PS: did you mod the terrans appropiatly in raceconfig? This could be the crash, since your entry still references the terrans, I think ... you just changed the dialoguetag. You need to create a nolor race or mod the terrans or any other race 