I see no problem in your last session (CoolVLViewer.log) since it logged off in under 4 seconds:
However, in the former session (CoolVLViewer.old), I can see a 3 minutes delay during the LLWorld class shut-down:
This could be an issue with the grid not replying to the viewer after it signaled its logging off procedure, but it's hard to tell where exactly it happens in the process. I added more log messages for the next releases, to try and spot the place where that glitch happens. It's however probably a grid-specific issue (I can't see it happening myself on all the grids I could test the viewer onto).