Tom I loaded your 322 bar xml file. Here is what I got.
1. all of the chords on the chord sheet were correct all the way to 322.
2. Track 1 was a midi track labeled cello 43 BUT there were no midi notes for the melody.The same issue with the shorter song you sent. I was able of course to load the short song into BIAB and there WAS a melody,grrr.
3. I generated a RT and it does it in 2 parts
A. Bar 1-239
B. bar 241 to the end. yes ther's agap between 240-241. Bar 240 is empty
C. bar 241 per the pdf should still be Dm but isn't
4. Regenerating makes no change
5. adding the Dm chord on all measures has no effect.
My conclusion:
1. RB can't properly open XML files no matter what length.
2. It can do songs from scratch or cut/paste past 235 and does generate properly.
Please send you XML file to the Foggle's to see if their results match mine. The variable I can't test is the XML file. A known good one would be helpfull.

John
ESI Gigaport HD+
Lenovo Turion II /4 Gig Ram/ Win7x64 be
15.6" Monitor
"The only Band is a Real Band"
www.wintertexaninfo.com/BANDS/JohnnyD.php