My mdi project worked fine until recently.? I don't know what I may have changed.
Previously, I could start up the program (not already running) with a double-click on a (pdf) file.? This is still OK.
However, previously, I could start up a second document by double-clicking on another pdf (which would open the new doc, or else select the doc if it is already opened). Now, I get .net error 8001010d when starting the second document, although I can **still** open a second document from the running program's interface.
The program uses a mutex to start up if the program is not running, and not start up another instance of the program if it is already running.