XnView Software

Apologies for the late reply (I forgot to assign notifications!)

Well, it was happening on every .gif with more than one frame. Basically if it had animation it would crash XnViewMP.
It's stopped doing it now... and the only thing that's changed has been the installation of newer Nvidia drivers. My ...

I'm also getting crashes when (re-)opening gifs. I searched and found this thread which is exactly what happens on my system.

I'm running XnViewMP 0.78 x64 on Win7 x64

Yes SAI is very popular now (I own it myself! :) and for many years it's been an annoyance that Windows Explorer (and every thumbnailing utility actually..) is unable to display its thumbnails.
Like you said, the only way to view thumbs for .sai is via the built in file browser.

So yea, I'm just ...

Yes, CLIP STUDIO / Manga Studio files would be an amazing addition!
The CLIP STUDIO application has just recently been released in English (formerly Japanese only), so I imagine it will become much more popular. It's really an incredible digital art suite.

Xnview, there's some (large) sample .lip ...