David,
The master GDL can happen when library parts of the same name come from different editions of archicad. Several releases back Graphisoft US started posting on their technical resources website
tr.graphisoftus.com
pla's of past libraries starting with AC6. The library parts in these plas had their names altered so that when loading them with other AC libraries the often problematic (crashing) sometime fatal MASTER_GDL___.... errors won't occur. These naming conventions have made our library management far simpler as well as allowing one to continue working with a file started in an older version of AC and still take advantage of new features and use simultaneously parts from the newer library. Keep the old parts and continue on with the new. replace old ones at your leisure.
You could look in your library report to find the location of the duplicate parts. Easier, and probably more useful in the long run is to
1. download the AC7 library pla from
tr.graphisoftus.com
2. load it, along with your AC9 library (see screen shot). You may want to start fresh with a new copy of your AC7 file. You can use parts from whichever library best suits your purpose. with no compatibility problems.
Let us know how it goes.
Erika
Architect, Consultant
MacBook Pro Retina, 15-inch Yosemite 2.8 GHz Intel Core i7 16 GB 1600 MHz DDR3
Mac OSX 10.11.1
AC5-18
Onuma System
"Implementing Successful Building Information Modeling"