I try to associate one ELF file with both of my MicroBlaze processors under Design Sources.
Then I associate a different ELF file with both processors under Simulation Sources.
I click OK to close the "Associate ELF Files" dialog box.
Then I again go to the Tools -> Associate ELF files option and find that one of the associations is missing.
The TCL Console shows the right command for association but the GUI doesn't show one of the associations under Design and Simulation Sources.
This behavior will occur if you associate the same ELF file with both cores in a dual MicroBlaze design.
To work around it, create a copy of the ELF file and rename the second file so that both can be used.
This issue is fixed in Vivado Design Suite 2014.2.