Error: Attempt to install an existing message block: IDL_MBLK_DICOMEX.

Problem:

Attempting to create an IDLffDICOMEx object results in an error like:

Attempt to install an existing message block: IDL_MBLK_DICOMEX.
Error: MC_Library_Initialization failed
Dynamically loadable module failed to load: DICOMEX.

The problem may be caused by corrupted local user IDL DICOMEx configuration files.

Solution: 

If the problem is caused by corrupted local user IDL DICOMEx configuration files, then one approach to fix this problem is to rename or delete the user's local IDL DICOMEx configuration folder. This will allow IDL to create a new default copy of the local configuration files at the time a new IDLffDICOMEx object is instanciated.

Instructions to correct corrupted local user IDL DICOMEx configuration files:

1.) First, exit out of any IDL sessions.

2.) Find the user's local IDL DICOMEx configuration directory under the user's home directory tree. The location of this directory also depends upon the operating system and version of IDL.

To find the local DICOMEx configuration directory for your IDL session, issue the following IDL command:

PRINT, FILE_DIRNAME( DICOMEX_GETCONFIGFILEPATH() )

For example, for a user named "joeuser" using IDL 8.2 on Windows 7, the path returned might look like this: 

C:\Users\joeuser\.idl\dicomex-1-400

3.) After the user's local "dicomex-..." directory is located, (delete or) rename the folder to disable it. For example, you could rename the directory by adding a ".bad" extension to the directory name:

C:\Users\joeuser\.idl\dicomex-1-400.bad

After this directory is renamed or deleted, the next time an IDLffDICOMEx object is instanciated, a new local DICOMEx configuration folder will be created, containing a copy of system IDL DICOMEx configuration files (obtained from the IDL product installation).

Hopefully, after the local user IDL DICOMEx configuration files are replaced, the original problem will be resolved.