I too was very tired of waiting 5 min to play a simple playlist, or even a single song for that matter.
I was about to set up my Linux box for just media because of this glitch.
I noticed while it was in "Updating" mode one day that down in the lower right corner I hovered mouse over that to get full description of what it was updating...Turns out it was my pictures.
I am an amature photographer and add pictures (sometimes 100's) on a daily ...well weekly ,basis. They are large RAW NEF formats. Do not know if it was the large format or just the 230gb of pics, but this worked for me.
Open WM - left side of window is the library column. in order mine is Library-Playlists-Music.
under music is Videos-pictures -recorded tv etc.
right clicked pictures- left click manage picture library-highlighted my picture location and clicked "remove"
This seemed to work so far to solve the updating issue.
There is a draw back. You will no longer be able to access your pictures from start and clicking on pictures. Obviously a mistake in start menu programing and sharing. Ie. that link is only valid if you share or let WM DB your pics. So easy start- click
/pictures is only an option if you do not mind waiting 5-10 min to play music while WM updates totally unrelated picture libraries. So you exclude pictures from the library , and then when you click start and then pictures, pictures it is empty, hahaha Awesome
MS stuff here.
So my fix for this- I clicked Start/ my name/ and then you will see pictures folder here.left click and Drag this folder down to the start button/ it should open up the start menu / then drag the folder to the top of the menu where if you release your mouse
button it should "pin" the folder there giving you quick access again to your actual pictures directory. Just my fix,and I can live with that for easy enough access without navigating all over the place, and it seems to be going ok and I now do not have to
wait the better part of 5 min. to play a song or playlist in WM.
Hope this helps.