in BC17 under Feature Management You have possibility to enable Feature Update: Write longer item references.
What it does is, that it copies entries from table Item Cross Reference (5717) to table Item Reference (5777).
So system now uses new table 5777 to find item's with cross references (look in table Sales line and You find Item Reference fields in addition to Cross-Reference fields we have had for years).
Biggest difference between the tables is that field(6; "Reference No."; Code[50]) is 30 characters longer than before.
Interesting fact:
From Item LIST searching for action "cross" an action Item references opens new table 5777 and from Item CARD searching for action "cross" an action Cross references opens old table 5717.
I presume it's a bug and not a feature...but You never know :-)