It seems Firefox 4 (final) has some problems with its sqlite files in the profile directory. It can't read bookmarks and history file created with 3.6 (places.sqlite), then removes the file. It creates a new empty file, but can't append new history entries to it. Visiting any URL is very slow, it looks like FF is trying to update the file but fails repeatedly. The same problem is with cookies.sqlite. My guess is there is a problem with the new WAL mode of sqlite used in FF4. The file places.sqlite-wal and -shm is always empty, which seems wrong. Also, the documentation to WAL mentions shared memory support is required from the VFS. Does win98 or kernelex provide this? Can it be added?