Commented out gui_disk_image_change(), gui_lock() and gui_unlock() from disk.c. Problem didn't go away.
Code:
PUAE 2.0.2
Build date: Feb 15 2010 13:31:39
SDLGFX: Initialized.
SDLGFX: Using SDL version 1.2.13.
SDLGFX: Display is 32 bits deep.
SDLGFX: Found screenmode: 1440x900.
SDLGFX: Found screenmode: 1024x768.
SDLGFX: Found screenmode: 832x624.
SDLGFX: Found screenmode: 800x600.
SDLGFX: Found screenmode: 720x400.
SDLGFX: Found screenmode: 700x525.
SDLGFX: Found screenmode: 640x512.
SDLGFX: Found screenmode: 640x480.
SDLGFX: Found screenmode: 640x400.
SDLGFX: Found screenmode: 640x350.
SDLGFX: Found screenmode: 576x432.
SDLGFX: Found screenmode: 512x384.
SDLGFX: Found screenmode: 416x312.
SDLGFX: Found screenmode: 400x300.
SDLGFX: Found screenmode: 360x200.
SDLGFX: Found screenmode: 320x240.
SDLGFX: Found screenmode: 320x200.
SDLGFX: Found screenmode: 320x175.
Found 0 joystick(s)
Found x11pc raw keyboard mapping
Using cooked keymap
Opening cfgfile '/home/uae/.uaerc'...okay.
Testing the RDTSC instruction ... done.
TSC frequency: 2393.500000 MHz
Found x11pc raw keyboard mapping
Using cooked keymap
Found x11pc raw keyboard mapping
Using cooked keymap
Entered action_replay_load()
ROM loader..
SDLGFX: Added P96 mode: 320x200x32
SDLGFX: Added P96 mode: 320x200x8
SDLGFX: Added P96 mode: 320x240x32
SDLGFX: Added P96 mode: 320x240x8
SDLGFX: Added P96 mode: 320x256x32
SDLGFX: Added P96 mode: 320x256x8
SDLGFX: Added P96 mode: 320x400x32
SDLGFX: Added P96 mode: 320x400x8
SDLGFX: Added P96 mode: 640x350x32
SDLGFX: Added P96 mode: 640x350x8
SDLGFX: Added P96 mode: 640x480x32
SDLGFX: Added P96 mode: 640x480x8
SDLGFX: Added P96 mode: 640x512x32
SDLGFX: Added P96 mode: 640x512x8
SDLGFX: Added P96 mode: 800x600x32
SDLGFX: Added P96 mode: 800x600x8
SDLGFX: Added P96 mode: 1024x768x32
SDLGFX: Added P96 mode: 1024x768x8
SDLGFX: Added P96 mode: 1152x864x32
SDLGFX: Added P96 mode: 1152x864x8
SDLGFX: Added P96 mode: 1440x900x32
SDLGFX: Added P96 mode: 1440x900x8
SDLGFX: Added P96 mode: 832x624x32
SDLGFX: Added P96 mode: 832x624x8
SDLGFX: Added P96 mode: 720x400x32
SDLGFX: Added P96 mode: 720x400x8
SDLGFX: Added P96 mode: 700x525x32
SDLGFX: Added P96 mode: 700x525x8
SDLGFX: Added P96 mode: 640x400x32
SDLGFX: Added P96 mode: 640x400x8
SDLGFX: Added P96 mode: 576x432x32
SDLGFX: Added P96 mode: 576x432x8
SDLGFX: Added P96 mode: 512x384x32
SDLGFX: Added P96 mode: 512x384x8
SDLGFX: Added P96 mode: 416x312x32
SDLGFX: Added P96 mode: 416x312x8
SDLGFX: Added P96 mode: 400x300x32
SDLGFX: Added P96 mode: 400x300x8
SDLGFX: Added P96 mode: 360x200x32
SDLGFX: Added P96 mode: 360x200x8
SDLGFX: Added P96 mode: 320x175x32
SDLGFX: Added P96 mode: 320x175x8
CBuilding CPU table for configuration: 68000 prefetch 24-bit
1876 CPU functions
Building CPU, 44316 opcodes (0 1 1)
CPU=68000, FPU=0, JIT=0.
CPUID level=10, Family=6, Model=7, Mask=6, Vendor=GenuineIntel [0]
JJCSDL: sound driver found and configured at 44100 Hz, buffer is 100 ms (17640 bytes).
BEAMCON0 0000 -> 0020
PAL mode V=50Hz H=15600Hz (227x312)
chipmem cleared
CIllegal instruction: 4e7b at 00FC0564 -> 00FC0582
PAL mode V=50Hz H=15600Hz (227x312)
Exception 3 (fc0fe3) at fc0fe0 -> fc081a!
PAL mode V=50Hz H=15600Hz (227x312)
Illegal instruction: 4e7b at 00FC0564 -> 00FC0582
PAL mode V=50Hz H=15600Hz (227x312)
Exception 3 (fc0fe3) at fc0fe0 -> fc081a!
PAL mode V=50Hz H=15600Hz (227x312)
Illegal instruction: 4e7b at 00FC0564 -> 00FC0582
PAL mode V=50Hz H=15600Hz (227x312)
Exception 3 (fc0fe3) at fc0fe0 -> fc081a!
PAL mode V=50Hz H=15600Hz (227x312)
Illegal instruction: 4e7b at 00FC0564 -> 00FC0582
DCOP1LC: 00000420, COP2LC: 00c00276 COPPTR: 0000046c
DIWSTRT: 2c81 DIWSTOP: f4c1 DDFSTRT: 0038 DDFSTOP: 00d0
BPLCON 0: 0000 1: 0000 2: 0024 3: 0c00 4: 0011
and so on ...