I'm also experiencing this issue.
For me it started exactly after I upgraded 1.73 to 1.75 (I was prompted with instalation for 1.74, but the installer was for 1.75). Same with 1.76. The only difference is I don't get the "Failure to start Bitcomet Disk Boost Service" prompt anymore, although it always says the service is not running.
The only solution was to set the program itself to run as admin, but there are some side effects, like having to open a .torrent file through the program, because simply clicking on one does open BitComet, but doesn't show up the torrent task window.