Chinese Pinyin IME stops functioning after a while

(thought I had posted this question - was it removed by the moderator for
some reason?)

After I have been typing using pinyin input with the Microsoft IME in any
chatroom, or instant messenger or Hotmail for a while, the Chinese characters
cease, no pulldown box appears and the typed characters are echoed as
entered, but in an altered font. The Language bar still Shows 'CH' selected;
although I change back to english, and return to Chinese, close the
application and reopen it, I cannot restore the pinyin input process without
rebooting. In Word, however the IME still works.

I have a fully maintained Vista Business, and Office professional 2003.

Can anyone offer some solutions or work-around please (apart from copy-paste
from Word!!!) ?
--
�鬼 LaoGui