voodoo47: check your thief.log, maybe there will be some failures listed.
I've had a look through the THIEF.log file and no record of failures (annoying, as that would have been useful to debug), This is a strange bug indeed! I'll add in the log's starting info if you want to see:
: PID: 10360
: CPU: arch=x86-64 , fam=586 , cpus=8
: SIMD: SSE=3 , 3DNow=0 , MMX=1
: Large Address Aware is enabled.
: OS Version: 6.1.7601 Service Pack 1
: Desktop resolution: 1920 x 1080
: Virtual desktop resolution: 1920 x 1080
: -----------------------------------------------------------
: Command line: "C:\GOG Games\Thief Gold\THIEF.EXE"
: -----------------------------------------------------------
: CWD: C:\GOG Games\Thief Gold
: -----------------------------------------------------------
: App Version: Thief 2 Final 1.25
: --------------------- misc config -------------------------
: resname_base .\patches+.\tgpatch+.\res
: load_path .\patches+.\
: script_module_path .\
: movie_path .\movies
: mod_path usermods+hdmod+hdmod\t2skies+patches
: install_path .\
: language english
: game_screen_size 1920 1080
: game_screen_depth 32
: game_screen_flags 45
: game_full_screen 1
: game_hardware 1
: vsync_mode 3
: single_display_mode 3
: ui_scale_mode 2
: use_d3d_display
: framerate_cap 100.0
: SlowFrame 4
: SlowFrameUI 10
: force_32bit
: force_32bit_textures
: mipmap_mode 2
: lm_mipmap_mode 2
: lm_init_texmem 2
: lm_filter_margin 1
: disable_lightmap_aniso
: tex_edge_padding 2
: alpha_test_as_opaque
: default_alphatest_ref 1
: d3d_disp_enable_atoc 2
: d3d_disp_sw_cc
: d3d_disp_enable_hdr
: multisampletype 16
: postprocess 1
: d3d_disp_enable_distortionfx
: sfx_device 1
: sfx_channels 16
: sfx_vol_music 0
: sfx_vol_2d 0
: sfx_vol_3d 0
: game dark
: dark1
: obj_min -6144
: obj_max 2048
: max_refs 8192
: gui_font intrface\smalfont
: enhanced_sky 1
: new_mantle
: z_far 512
: wr_render_zcomp
: render_weapon_particles
: legacy_force_match_unrefs 0
: dark_zcomp_arm