This feature still exists. If you are starting up to the new Firefox start page, look for a session restore button below the search box.

Sometimes Firefox has trouble creating session history because of file permissions or a corrupted file.

These articles describe some file maintenance procedures you might try:

Firefox does not ask to save tabs and windows on exit >> Corrupted files

Firefox hangs >> Duplicate session restore files

Does any of that help?

Yes, that helps jscher, thanks a lot! Just tried it and your tip works.

This actually encourages me to maybe post another question about the freezing (cause my freezing is not like the hanging that's described in the articles you linked).

Thanks again.

You can also use "Firefox > History > Restore Previous Session" to get the previous session.

Another possibility is to use:

• Firefox (Tools) > Options > General > Startup: "When Firefox Starts": "Show my windows and tabs from last time"

Thanks corel, but Restore Previous Session is greyed out and hence doesn't work here. Your 2nd suggestion is exactly what jscher had recommended.