Vista - vista language pack problem

i installed multiple language packs for my pc. my preference is Trad Chinese but since a little while ago some of the messages suddenly were displayed in Arabic. i tried to change the language settings to English and same thing happened. it doesnt help also to changing it back to Chinese. i wonder if someone has come across this also? what should i do? thanks.

what is displayed in Arabic:
- the login screen at startup when user is asked to input password. the cursor in the input box is even on the right. the wrong password messages and password hints are all in Arabic
- windows auto updater. while all the options and buttons are in the user chosen language as they are in explorer.exe, all the info concerning the new and installed patches are in Arabic
- some, small number of error messages