Note this in the file user.cfg in your T2 install folder:
;Some video cards may not work properly with Thief 2
;including the intel 810 and the nVidia RIVA 128.
;To fix, remove the semicolon from the next line.
(so remove the semicolon from safe_texture_manager and try it).
There are other ways to fix this problem such as installing DDFIX. TTLG Legacy Gaming Technical Forum (or similar) may provide more options if the above doesn't work.
"What we've got here is a failure to communicate", the warden (Strother Martin), Cool Hand Luke