From time to time FPV will become very unresponsive for a period -- maybe 10 seconds.
Task manager suggests that it's busy working on pre-fetches. But it seems to want to complete ALL of the queued pre-fetch operations before it will respond to a whack of the space bar to display the next image. This doesn't appear to be the case all of time. It seems like the pre-fetch operations are non-interruptable some of the time. At other times, it will display the next image even though it appears to working through a list of pre-fetches simultaneously.
Disabling the pre-fetch option appears to solve the problem but I loose the benefits of the pre-fetch

I have tried turning off the GPU option and that didn't seem to help.
And although I have a 4 core system I do leave parallel pre-fetching off since that has caused other issues on this machine. Changing the more/less slider on the pre-fetch settings doesn't appear to make much difference.
If I hold down the space bar continuously, sometimes it will advance through the folder of images at around one per second. Other times, it will advance in bursts -- no new image for 10 seconds and then 10 images in 1 second. Again it suggests the pre-fetch thread is pre-empting the UI, sometimes.
I realize there has to be some locking and so forth but 10 seconds seems excessive on a reasonably fast machine -- Dell XPS 420 with 4MB RAM and two 7200rpm SATA drives (which have been defragged). It's a lot more than the time required to fetch and display one image.
Any suggestions for me? I'll respond promptly of you need any additional info.