I checked in the Windows Task Manager the status of the resources that CodeBlocks were using: CPU at 55% (also the CPU fan was working hard).
Also I unchecked the options "Update parser when typing" but the CPU did not fall under 55% ...
My CB has the same problem on both xp and vista.
disable "Follow GLOBAL includes"(in C/C++parser settings) will reduce the CPU usage in my case.
So I guess the code completion plugin caused the problem.
Build 6023 does not have this problem.
(BTW, I don't know much English, and I hope the above words are clear.)