Perhaps a look at your Windows Update history via Add/Remove Programs - check the updates box and then see if something was installed after the last known good configuration of Jeppview would offer more clues.
If there is a correlation, a system restore to times past may allow the software to run and point to a possible explanation. (solution may be another thing entirely)
Out of interest, on restart as I said Jeppview 'splash' appears with a message box saying 'readreg.exe' failed to initailise as the system is shutting down. Any clues there?
Your observation is what led me to think that the program was running but not having focus. The readreg errors lead me to the conclusion that there is a bug within Jeppview that may be related to a Windows issue.
I am not much help here, am I?
Good Luck!