Update:
I just tried the SEGA Dreamcast DCIE Import Enabler and Shenmue worked flawlessly. I think there might be some copy-protection on Shenmue PAL that causes it make the DC lock up when using the utopia boot disc.
If anyone has a similar problem with an import, then another boot disc might be the answer. Plus, I simply prefer this boot disc to the utopia one now. It seems to be a bit less hard on the laser, and there's no "loading sequence(s)" or progress bars after you remove the disc and put in your import. The DC simply starts the game.
I have a PAL DC but 2 of the games I want to play the most right now are imported from the States (Shenmue and JSR): the Utopia boot disc never works for me, it just stops loading at 83% every fucking time. I can't even make/buy a new one at the moment and it makes me so mad.
I'm playing ChuChu Rocket like there's no tomorrow tho.