Got this one recently (well, it might not be relevant any more, but it can happen again with some other class):

Booked LH U class, operated by Adria Airways (JP):
"Buchungsklasse n. meilenberechtigt", 0 miles.

They didn't map the booking class, but as JP doesn't have its own U class, they simply declared it as non-eligible for mileage accrual. The whole thing was quite painful as it cost me the FTL extension. In addition, I called the hotilne in December (when I already knew that my status depends on these two filghts) and they assured me that LH U on JP metal does give full mileage credit. Also, the M&M table of the time (it has changed since) didn't list any exceptions for the U class bringing 750 miles. Do you think I have a chance if I complain somewhere (in writing or by phone?)?