Hi
I've had a look at the thread over on sh404SEF forum when you first posted here and it is interesting to see what Shumisha had come up with. I've not had time to look at it really and I don't have a copy of sh404SEF anyway, hence my lack of reply.
I've been having a few issues myself during development which I will discuss over on the Anything Digital forum but suffice to say there may well be a problem with FAQ Slider or sh404SEF
but I'm a bit worried that it may in fact be a PHP issue. I've been able to reliably recreate the issues discussed
here.
Can you try the new FAQ Slider version and let me know if there is any improvement? Are you getting any core.xxx files generated on your server showing that PHP is exiting and producing a core dump?