I don't understand why they would. But you could always try. It'd be cool if they do. You, with your Slim, have every reason to upgrade to this anyway.
As I tried to say earlier, try patching to 3.52 M33-4 instead. Also, reformatting your memory stick could be helpful. If not, try restoring the system's default settings / formatting flash1. If that doesn't work either, I'd recover back to 1.50 and re-upgrade from there to get a clean flash, or just re-run the 3.52 M33 upgrade.