I have my Windows 7 desktop set to run a slideshow (shuffle turned on) with the contents of a folder that currently contains 148 photos. The problem is that every now and then, it stops cycling through them, and the Next Desktop Background item in the context menu is no longer there. Basically, it stops at a photo and unselects the rest of them. There doesn't seem to be any rhyme or reason as to when it happens; often, the slideshow will keep cycling even after a reboot, and sometimes it will just stop cycling for no apparent reason after a few days even with no reboots during that time.
Does windows have an upper limit to the number of photos that it can reliably handle in a desktop slideshow, or could it be one of the photos that it doesn't like that's causing that to happen?
I did an experiment where I changed my slideshow to show the pictures sequentially and change once a minute. I pulled half of them out and didn't see the problem even after a whole day of it being that way, so I put those back and pulled the others out. Still didn't see the problem (again, even after a whole day of it being that way), so I put all of them back. Still nothing (again, even after a whole day of it being that way). That tells me that the problem is not not with any of the pictures themselves; nor is it because of the settings that I used before (change once/hour and shuffle turned on).
After my computer rebooted because of an AVG update, the slideshow went from all pictures selected to just the current one. Given my previous experience, though, reboots are not the cause, because sometimes the slideshow selections survive a reboot, and sometimes they'll change to just the current picture after several days even without a reboot.