1.It's very probably that your problem isnt a result of GC but instead an external source, ie. virus, or plugins. Try uninstalling GC alltogether. If theres still a problem, you might want to check your protection, then check your start-ups, and disable anything that you don't know (research it, if its foreign to you). Then check your browser plugins and addons and look through your task manager for possible dll or exe processes relating to sound.
2.if you tried all this and it doesnt work, check your directX driver
3.or download directx10 and see how that runs for grandchase and try scanning your computer.
4.if none of these, help... i suggest you just restart ur whole computer(meaning like new pc with clean control panel and no virus+fast pc)