A bad bug in Gecko popped up today:
https://bugzilla.mozilla.org/show_bug.cgi?id=1489785
I tested a local 2.49.4 and didn't encounter it but to be on the safe side do not upgrade your OS yet. If it is too late and SeaMonkey becomes unusable shoot me a pm. I can provide a private 2.49.5 prerelease x64 only build if needed. Our new infrastructure is not yet ready.
FRG