It sounds that the user refresh parameter is having impact on the slideshow screen on 1.8.1 ..

In fact, on the user description screen, there is a refresh interval parameter. This parameter is refreshing the slide show.
I had a parameter set at 5 seconds. It means that it was restarting the slides show after 5 seconds.

ex :
My slideshow is composed of 3 slides of 20 seconds. It means a complete slideshow sequence is 60 sec.
With a settings to the user at 5 sec, i was only seing the first slide 5 seconds, then it was blinking, and displayed the same slide again.
With a setting to the user at 30 sec, i was seing the first slide 20 seconds, then the 2nd slide 10 sec, then the slide show was restarting from the beginning.
With a setting to the user at 60 sec, i was seing all slides correctliy during 20 seconds.

I guess that the solution should be that the user settings is not used for refreshing in slideshow... That is my opinion but I am not skilled in PHP to help you more than that.