I run Thief 3 on Win 7 64 bit - no problems.
I have installed;
"Collective Texture Pack ver. 1.0.3.exe" (Thief Deadly Shadows texture
pack)
106MB.
The original creators site is closed buts its easy to find by Goggling
"Collective Texture Pack ver. 1.0.3.exe"
The other patch you have been referring to here is
"Thief 3 -fix bugs + Widescreen - Setup_T3SneakyUpgrade_1.1.3.1.exe"
I don't have that installed but I don't think it will clash with Texture
pack.
With your problem I would try e.g. Alt-tabbing out & back again.
Switching to Windowed (press alt-enter & again to restore)
Try different resolutions.
Right click the Games starting shortcut or exe & select Compatibility Mode
"Windows XP"
Perhaps live with it if you can see enough in the mouse movement 'flickers'
to select required option.
(\__/)
(='.'=)
(")_(") mouse (Hmmm? -Needs A Good Rub n Scrub-down)