I know this is an old post, but I am having the exact same problem, with the newest version of codeblocks.
In large projects with 1000 lines of code or more and a dozen or more source files, codeblocks user interface will Freeze every 30 seconds or so, and the freeze will last for as long as 8 seconds, it makes the UI almost un-usable, I am running on an AMD quad core with 4 gigs of memory, default codeblocks install, no customizations of special configurations...
I notice it does not do this on small projects at all. (2 to 3 source code files, about a hundred lines of code)
I disabled "Settings -> Editor -> Code-Completion and symbols browser -> Code completion -> Update parser when typing ..."
and it still freezes....
I am still try to find the cause, seems like it's parsing something intensive and it's not doing it in a separate thread, which is locking up the UI.