Riven X - Glitch approaching dome from Crater Island (can't access Fire Marble puzzle)

[Sarah]

While approaching the dome from Crater Island (crossing the bridge past Gehn's office), as soon as I step into the dome (after lowering the ladder), the game glitches and puts me on the other side of the dome (on the Main Island). This is important because it means I can't reach the other side of the dome to extend the bridge -- which makes it impossible to reach the top of the dome to access the Fire Marble puzzle.

I took a few screenshots to show the exact location (as well as the location it puts me in when it glitches.... which seems to be a nonexistant spot, I can only reach it via the glitch and when I turn around, it's gone, replaced with a normal view of the "control room" in the center of the dome):

About to enter the dome from the other side (Crater Island) (this is as far as I can go before the glitch occurs):
http://i.imgur.com/oR7wL.png

When I take one step forward, I end up here:
http://i.imgur.com/l2eF1.png

Looking to the left -- as you can see I'm back on the other side, on the Main Island (if I follow this path it leads me to the two steam-controlled levers which activate the bridges):
http://i.imgur.com/Oz4cF.png

I'm running Riven X 0.9.8

-MacBook
-2 GB
-NVIDIA GeForce 9400M
-256 VRAM
-10.6.8
-Steam version of Riven

Any help would be greatly appreciated! Thanks so much for the work you've put into this project, I've been having a blast.