Here is another bug i have nearly each time on two different games :
It happens on game loading. At a moment, the image flip (turn at 180°) and display some graphic bugs on Mac OS X interface, hiding the mouse.
Nothing is display on gdb and bt is :
(gdb) bt
#0 0x940a46fd in glgProcessColor ()
#1 0x9409621a in glgProcessPixels ()
#2 0x0de71b33 in gldGetTextureLevel ()
#3 0x0dce21d2 in glTexSubImage2D_Exec ()
#4 0x92b2edaa in glTexSubImage2D ()
#5 0x0003b040 in gl_load_frame_buffer ()
#6 0x0002c260 in pvr2_frame_buffer_to_render_buffer ()
#7 0x0002c40f in pvr2_display_frame ()
#8 0x0002c5ee in pvr2_scanline_callback ()
#9 0x00011838 in event_execute ()
#10 0x000504c5 in sh4_translate_run_slice ()
#11 0x00012b2f in sh4_run_slice ()
#12 0x00010a1e in dreamcast_run ()
#13 0x9280bbd3 in __NSFirePerformTimer ()
#14 0x9082dce2 in __CFRunLoopDoObservers ()
#15 0x9082cd84 in CFRunLoopRunSpecific ()
#16 0x9082ca42 in CFRunLoopRunInMode ()
#17 0x92ded878 in RunCurrentEventLoopInMode ()
#18 0x92deceb9 in ReceiveNextEventCommon ()
#19 0x92decdd9 in BlockUntilNextEventMatchingListInMode ()
#20 0x93272f45 in _DPSNextEvent ()
#21 0x93272b37 in -[NSApplication nextEventMatchingMask:untilDate:inMode:dequeue:] ()
#22 0x9326c8c4 in -[NSApplication run] ()
#23 0x00056e48 in gui_main_loop ()
#24 0x00007444 in main ()
I hope this will help (again)