If Oracle made it easier to access their bug database, I would search for a solution, or post a nice report there, but as it is, I'll just post it here. Hopefully, this does not violate the code of conduct for Certified Professionals.

SQL> select * from dual where (dummy,dummy) in (((select dummy,dummy from dual)));

select * from dual where (dummy,dummy) in (((select dummy,dummy from dual)))
              *
ERROR at line 1:
ORA-00600: internal error code, arguments: [kkqtnlop2Cbk : 1], [], [], [], [],
[], [], []

Note that this actually crashes Oracle. Also note that it works as expected when there is only one column in the inline view, or if there is one pair less of superfluous brackets around it.

Update: While it crashes my 10g R2 XE (on Debian and on Windows), R1 seems safe...