Hi,
After I installed 0.7.15 on top of 0.7.14 and started the program, I only got the splash screen and then nothing. In Process Explorer I could see that calibre.exe and calibre-parallel.exe (2 times while in 0.7.14 it is initially 4 times) were loaded, but there was no way I could get the program on top.
Removed 0.7.15 and re-installed 0.7.14 and had no problems, program was working fine, could import books, etc.
Decided to remove 0.7.14 and re-install 0.7.15 and then I got the splash screen and I could import a book but that never came to an end.
After more testing I finally have 0.7.15 working but only after I cleared the box for "Limit the max. simultaneous jobs to the available CPU cores". I was triggered by this option as the initial startup of 0.7.15 only showed 2 times calibre-parallel.exe while I always saw that this program was initially loaded 4 times.
Hope this helps for somebody else having problems with 0.7.15
Note that this is the first time since using 0.7.xx I have problems with an upgrade to a newer version...not bad..
Regards...Dick