Confirmed with Oracle through Metalink support log that this is indeed a bug.

Oracle have also confirmed this as a bug in:
10.2.0.4
11.1.0.6
11.1.0.7 (where I found it)

The fix for this is not yet included in 11.1.0.7 patch bundles.

Workaround:
Do not use ANSI JOINS.
Prefix the column name.
Use 10.2.0.3.

This Oracle port is going to be fun...

Andy