Hi there, Hope someone can help, running Firefox 57.0.4 32bit and we are having a strange issue where Firefox refuses to start but unresponsive process consumes a lot of CPU. The problem appears to be with the Startup Cache or "fastcache" as if the following file is removed Firefox is then able to start: "C:\Users\USERNAME\AppData\Local\Mozilla\Firefox\Profiles\PROFILENAME\startupCache\startupCache.4.little" Firefox then creates another file on exit, but after some time the issue returns and we have to again remove the "startupCache.4.little" file. One workaround that does work is to start Firefox with the -purgecaches switch which clears the cache on startup (including the startupCache.4.little file) I am able to reproduce the issue by copying the startupCache.4.little from a profile with the issue. Not sure what is actually causing the problem with the file all we know is that removing the file fixes the problem. Any insight on this would be appreciated or/and does anyone know if there is a away of debugging Firefox to see what is actually happening or any ideas? Thanks in advanced