fatInitDefault() failing with IOS58 and USB

[Stealth]

After having installed IOS58 and HBC1.0.8, I've found that the fatInitDefault() call in my program always fails when it's run from my USB drive. It returns 0 when there is no SD inserted, but when there is, it outright crashes ("Exception (DSI)"). It seems to work fine when run from the SD, even with the USB drive plugged in and turned on, and everything else that was working from USB before the update still does. The only code that precedes the call are the basic init calls for controller input and video (not trying to use any other USB devices), and the first time this happened, it happened on a build that hadn't been recompiled since it last worked from USB

What could be going wrong?

Edit:

everything else that was working from USB before the update still does

Actually, I have to take that back. Some things I hadn't tried again yet did stop working- Super Mario War now reports that it can't find its files, EEEEK!EEEEEK!HOOOOOOK!!now reports some error off the top of the screen that I can't see, and HBB now crashes on some downloads (seems like larger ones?).

Also, obvious typo.. I meant "HBC1.0.8", not "HBB1.0.8"

Found this, on the HBC bug tracker, too:

Comment by dhewg (dhewg) - Monday, 16 August 2010, 13:15 GMT-7
got a similar report on irc. looks like the new usb code in libogc is unable to mount every drive out there.

which is in response to this:

If i switch from sd to usb everything is fine. I can see and load the applications from the drive. But if i switch back to sd the usb drive shuts down after a couple of seconds.

Edit2:
Well, seems like my own problem was solved by adding a sleep() before fatInitDefault(). Doesn't explain what happened to HBB, but this may still be an issue with some other apps run from USB with the new IOS