Try closing all your folders before you shut down.  I read somewhere that Poser scans all top level folders and all the ones that are open one level down.  So if you have all your folders open in a file system like  this:

 

Poser 8

     Figures

          DAZ People, Freak, Freak 4, Victoria 3, Victoria 4, Michael 4, Matt, Maddie...

it has to read the Poser 8 directory and all the figures before it opens.  If you close all your folders so that all that shows is

Poser 8

under each category (figures, poses, hair, hands, etc.) when you shut down, then all it has to read is Poser 8.  There's nothing open below that level.  Sometimes it's slower than other times, but when I do this, on a slow open, my 45 gig runtime opens in about 10 seconds.  When it's fast, it opens in about 3 seconds.