JavaFX Blocks EXCEL DDE Applications

ISV rolled out their first JavaFX application to their customers. The
customers use Excel DDE to transfer information between Excel and their
financial applications. They report the JavaFX application hangs Excel. When
the JavaFX application exits, Excel runs normally.

The customer provided a reproducible testcase consisting of
1. HelloWorldMain.java
2. cqg_dde_example_link.xlsx

Here are the steps to reproduce the testcase.

Step 1. Open cqg_dde_example_link.xlsx in Excel. The file has just one DDE
cell in it. Without JavaFX running Excel will immediately report that you do
not have the CQGPC.exe which is fine. This is the expected behavior when
CQGPC.exe is missing.

Step 2. Close Excel and start the JavaFX program, HelloWorldMain.java.

Step 3. Open cqg_dde_example_link.xlsx in Excel. Excel will just hang there
indefinitely.

Step 4. Close the JavaFX program, and Excel runs as expected.