Yesterday, I had this same warning suddenly show up and shut down JTAlert. I rebooted the computer, restarted JTAlert and the problem continued. It would pop up about 1 minute into program start. Vers .15 has performed flawlessly until yesterday. The only variable in operation was that I had turned off DXSummit submission. I turned it
back on but that did not fix the problem.
Finally, I renamed the JTAlert "user" directory to JTAlert-old and reloaded the .15 version. Of course I had to go in and reconfigure all of the settings but after about 15 minutes (helped by the fact that I use PrntScr to make record of all of the critical settings) I was back up and running. I ran the program for about an hour with no glitches.
I am not sure if turning off DXSummit submission may have corrupted the user files or not?
I will not mess with that setting again as I am quite happy to be back up on FT8.
As Mike said, hopefully corrected in a future version.