Search function too slow/blocks UI

First of all, I really like foxit's size and speed.
One thing I particularly love foxit is the ability to change the background and text color.
Thanks!

One problem here:
When I use search (Ctrl-F) to find a word in the current page, it takes a long time (more than 20 seconds).

what is more, it can not find the desired target, such as 'is' in long pdf file.

foxit block user interface (using the same thread for searching?) to search, and user has no option to stop a time-consuming search. Mouse is just gone..

I am using foxitreader 1.3 beta 0704 on windows 2003 server.